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ELECTRIC  LIGHTING  BY  INCANDESCENCE. 


SAWYER. 


ELECTRIC  LIGHTING 


BY 


INCANDESCENCE, 


AND   ITS 


APPLICATION    TO    INTERIOR   ILLUMINATION. 


A   PRACTICAL    TREATISE. 


WITH  96  ILLUSTRATIONS. 


BY 

WILLIAM    EDWAKD    SAWYER 


FOURTH  EDITION. 


YOEK  : 
D.   YAN    NOSTRAND,    PUBLISHER, 

23  MURRAY  STREET  AND  27  WARREN  STREET. 
LONDON  :  E.  &  F.  N.  SPON,  16  CHARING  CROSS. 

1887. 


I 


e^W,'  tt 


Copyright, 

1881, 
By  D.  VAN  NOSTRAXD. 


H.  J.  HEWITT,  PRINTER,  27  ROSE  STREET,  NEW  YORK. 


PREFACE. 


THE  subject  of  electric  lighting  by  incandescence  is  one 
of  general  interest.  Its  brilliant  promises  have  ex- 
cited the  curiosity  and  the  anticipations  of  the  public 
to  a  degree  almost  unprecedented  in  the  history  of  inven- 
tion. But  beyond  the  threshold  of  the  laboratory  its 
processes  are  unknown,  and  information  which  would  be 
of  service  to  experimentalists  is  withheld. 

My  purpose  in  preparing  this  work  is  not  alone  to 
show  the  state  of  the  art  in  its  practical  applications, 
but  also  to  indicate  the  direction  in  which  the  laborer  in 
science  is  most  likely  to  attain  success,  and  to  impart  an 
accurate  conception  of  the  principles  underlying  the  em- 
ployment of  electricity  for  interior  illumination. 

Special  description  of  lighting  by  the  voltaic  arc  is 
omitted,  for  the  reason  that  the  subject  is  fully  dis- 
cussed in  numerous  text-books  readily  obtainable,  and 
because  there  are  few  cities  in  which  this  form  of  light- 
ing may  not  now  be  seen  in  operation ;  while  to  the 
subject  of  electric  generators,  which  constitute  the  be- 
ginning and  the  end  of  any  system  of  lighting,  consider- 
able space  is  given. 

5 

464519 


6  PREFACE. 

Those  who  expect  to  find  these  pages  the  vehicle  of  a 
theory  will  be  disappointed.  Those  who  expect  to  find 
them  devoted  to  criticism  of  the  labors  of  other  experi- 
mentalists will  be  equally  disappointed. 

In  the  position  of  an  impartial  student  and  observer 
I  have  sought  less  to  indicate  defects  than  to  exhibit 

accomplishments. 

WILLIAM  EDWARD  SAWYER. 

NEW  YORK,  January  15,  1881. 


CONTENTS. 


PAGE 

INTRODUCTORY,        .        *•.'-.        * 9 

CHAPTER   I. 
Generators  of  Electricity,        .        .        .        .        .        .        .        .        .13 

CHAPTER  II. 
Generators  of  the  Gramme  Type,  .  ...  ,  .  .  .  .27 

CHAPTER  III. 
Generators  of  the  New  Siemens  Type,  .......  37 

CHAPTER  IV. 

Incandescent  Lamps,       .        ....        .  .  .54 

CHAPTER  V. 
Carbons  for  Incandescent  Lighting, 64 

CHAPTER  VI. 
New  Forms  of  Lamps,  .  .  .  .  •  .  .  .74 

CHAPTER  VII. 
New  Forms  of  Lamps  (Continued),  ....  .  .  • .  .  91 

CHAPTER  VIII. 
Preservation  of  Incandescent  Carbons, .  105 

CHAPTER  IX. 
Division  of  Current  and  Light,  .  .  . .  > H5 

CHAPTER  X. 
Regulators  and  Switches •  ,  •  . .  129 

CHAPTER  XI. 
General  Distribution,  .  150 

CHAPTER  XII. 
Commercial  Aspects, 188 


INTRODUCTION. 


WHEN  the  free  ends  of  two  conducting  wires  con- 
nected with  the  terminals  of  a  galvanic  battery, 
or  other  generator  of  electricity,  are  brought  together, 
the  circuit  of  the  generator  is  completed,  and  a  cur- 
rent of  electricity  more  or  less  powerful,  according  to 
its  quantity  and  electro-motive  force,  traverses  the  ele- 
ments of  the  generator  and  the  conductor  uniting  its 
terminals.  This  conductor  offers  a  certain  resistance  to 
•the  passage  of  the  current  which  may  generally  be 
disregarded.  The  generator  oifers  a  considerable  resist- 
ance, and  the  current  appears  as  heat  in  its  elements, 
for  the  reason  that  the  current  is  divided  between 
the  generator  and  the  conductor  in  proportion  to  their 
respective  resistances  ;  and  the  calorific  effects  of  current 
in  any  conductor  are  proportional  to  its  value  in  that 
conductor.  If,  now,  we  separate  the  ends  of  the  con- 
ducting wires,  the  movement  of  separation  involves  pri- 
marily a  poor  connection  at  the  points  of  contact,  and 
a  poor  connection  means  resistance ;  hence  the  former 
relations  of  the  generator  and  the  conductor  are  dis- 
turbed, and  the  current  being  distributed  exactly  in 
proportion  to  the  resistance  of  any  part  of  the  circuit, 
a  less  proportion  is  found  in  the  generator  and  the 
remainder  is  concentrated  at  the  imperfect  points  of 


10  INTRODUCTION. 

contact,  where  it  produces  heat  sufficient  to  fuse  and 
then  to  vaporize  them  ;  and  as  the  vapor  of  a  conductor 
is  also  a  conductor  of  electricity,  the  current  traverses 
the  break  between  the  points  of  contact,  as  they  are 
drawn  apart,  to  a  distance  commensurate  with  the  in- 
tensity or  electro-motive  force  of  the  current.  The  va- 
porized conductor  uniting  the  points  of  contact  con- 
stitutes the  voltaic  arc,  the  most  brilliant  and  dazzling 
of  all  artificial  lights.  In  the  Serrin,  Siemens,  Jabloch- 
koif,  Brush,  and  other  lamps,  the  arc  is  formed  between 
the  ends  of  carbon  rods  or  pencils  ;  and  the  light  is  more 
intense  and  economical  when  the  distance  between  the 
carbons  is  slight  and  the  current  great  in  quantity  than 
when  the  reverse  is  the  case. 

The  vo]taic  arc  is  the  most  economical  of  electric 
lights  ;•  and  in  the  illumination  of  large  open  spaces, 
and  for  all  purposes  requiring  much  penetrative  power, 
it  will  doubtless  maintain  its  supremacy.  In  many 
cases  of  experimental  test  it  has  developed  a  light  of 
from  1,000  to  2,000  candles  per  horse-power  of  force 
expended  in  driving  the  generator,  the  cost  of  which  in 
large  steam-engines  is  less  than  one  cent  per  hour. 

In  both  the  voltaic  arc  and  the  incandescent  forms 
of  lighting  the  dynamo,  or  the  magneto-electric,  type  of 
generator  is  now  universally  employed.  Each  type  of 
machine  is  designed  to  transform  mechanical  force  into 
electricity.  The  magneto-electric  machine  is  that  in 
which  the  magnetic  field  is  derived  from  a  permanent 
magnet.  The  dynamo-electric  machine  is  that  in  which 
the  permanent  is  replaced  by  an  electro-magnet.  Both 
operate  upon  the  same  principle — that  the  cutting  of  a 


INTRODUCTION.  H 

line  of  magnetic  force  by  an  endless  conductor  of  electri- 
city, constituting  a  closed  circuit,  induces  in  the  latter  a 
current  whose  direction  is  determined  by  the  direction 
of  motion  of  the  conductor,  or  the  direction  of  polarity  of 
the  magnetic  lield.  The  machines  of  Pixii,  Clarke,  Nol- 
let  and  Van  Malderen,  Ladd,  Wilde,  and  others  are  ex- 
amples of  both  magneto  and  dynamo-electric  generators, 
but  they  have  all  succumbed  to  the  superior  apparatus 
of  the  present  day.  Of  these  old  machines  we  shall  con- 
sider the  generator  of  Wilde  as  embodying  a  principle 
which  is  destined  to  play  an  important  part  in  the 
utilization  of  electricity  for  the  purposes  of  domestic 
illumination. 


CHAPTER  I. 

GENERATORS   OF   ELECTRICITY. 

THE  value  of  a  pound  of  coal  in  mechanical  energy  is 
about  12,000,000  foot-pounds  ;  the  value  of  a  pound 
of  zinc  is  about  1,845,000  foot-pounds.  The  cost  of  a 
pound  of  zinc  is  about  twenty -live  times  the  cost  of  a 
pound  of  coal.  With  this  great  discrepancy  between 
the  energy  and  cost  of  the  one  and  the  energy  and  cost 
of  the  other,  and  after  making  due  allowance  for  all  the 
facts  favorable  to  zinc,  it  is  clear  that  in  electric  lighting, 
at  least,  the  period  of  usefulness  of  the  galvanic  battery 
has  passed,  not  to  return.  The  discovery  by  Faraday, 
in  1831,  of  magneto-electric  induction,  and  the  construc- 
tion by  Pixii,  a  year  later,  of  the  first  magneto-electric 
machine,  mark  the  beginning  of  the  era  of  conversion  of 
mechanical  power  into  electricity  ;  but  we  shall  not  at- 
tempt to  describe  the  efforts  of  the  earlier  experimenters, 
who,  although  far  in  advance  of  their  times,  made  little 
progress  toward  the  realizations  of  the  present  day.  Af- 
ter Pixii  came  Saxton,  in  1833  ;  Clarke,  in  1836  ;  Nollet 
and  Van  Malderen,  in  1849  ;  and  Holmes,  in  1852,  all  of 
whom  employed  the  magneto  -  electric  principle.  In 

13 


w 


14 


ELECTRIC  LIGHTING  BY  INCANDESCENCE. 


1857  the  Siemens  armature  was  invented,  and  subse- 
quently, in  1866,  Wilde  constructed  his  remarkable 
machine  (Fig.  1). 


Fig.  1.  The  Wilde  Machine. 

The  Wilde  machine  consists  of  a  Siemens  armature 
whose  electro-magnetic  field  of  force  is  sustained  by  an 
exciting  machine  of  the  magneto-electric  type.  It  is. 


GENERATORS  OF  ELECTRICITY.  15 

therefore,  a  double  machine,  each  part  of  which  is  pro- 
Aided  with  a  Siemens  armature,  whose  advantages  are 
that  it  occupies  but  little  space,  and  may  therefore  be 
rotated  in  a  magnetic  field  of  maximum  intensity  ;  and 
wThose  disadvantages  are  the  high  speed  of  rotation 
necessary,  and  excessive  heating  by  reason 
of  the  rapid  changes  in  its  molecular  struc- 
ture consequent  upon  the  rapidity  of  its  ro- 
tation while  cutting  the  lines  of  magnetic 
force.  Between  the  opposite  poles  of  a  com- 
pound permanent  horseshoe  magnet  the  ar- 
mature is  placed,  and  its  rotation  is  effected 
by  means  of  a  belt  passing  over  the  pulley 
shown  in  Fig.  2.  The  Siemens  armature 
has  not  gone  out  of  use,  for  its  simplicity 
and  cheapness  of  construction  continue  to 
commend  it.  In  electro-plating  and  labora- 
tory work  it  finds  constant  employment. 

Primarily,  the  Siemens  armature  consists 
of  a  roller  of  wrought  or  cast  iron  in  which 
deep,  longitudinal  grooves  are  cut,  whereby 
its  section  is  reduced  to  a  form  similar  to 
that  of  the  letter  H.  Lengthwise  in  these 
grooves  the  induction  helix  of  insulated  wire 

Fig.  2.  Siemens 

is  wound.     In  Fig.  3  we  have  a  section  of       Armature. 
the  armature  and  the  field  magnet  polar  extensions  of 
the  lower  machine. 

In  the  upper  or  magneto-electric  machine,  the  induc- 
tive action  is  derived  from  the  permanent  magnets  M, 
whose  extremities  are  in  contact  with  the  soft-iron  polar 
extensions,  m  n,  forming  the  sides  of  a  socket  within 


16 


ELECTRIC  LIGHTING  BY  INCANDESCENCE. 


which,  the  armature  rotates.  The  current  generated  in 
the  armature-coil  flows  from  the  commutator  to  the 
binding- screws  p  q,  which  are  the  terminals  of  the  large 
electro-magnet  coils,  A  B,  through  which  the  current 
circulates.  The  lower  extremities  of  the  large  magnet 


Fig.  3.  Section  of  Siemens  Armature  and  Field. 

are  in  contact  with  two  iron  polar  extensions,  T  T,  sepa- 
rated by  a  mass  of  diamagnetic  metal,  i ;  and  the  second 
Siemens  armature,  of  large  size,  furnishes  the  current 
for  external  use.  F  is  the  bearing  of  the  armature-shaft. 
A  B,  M  N  (Fig.  3)  represent  the  socket  within  which  the 
armature  revolves,  the  portions  A  B  being  of  iron  and 
M  N  of  brass  or  other  diamagnetic  material.  By  em- 
ploying the  current  induced  in  the  armature  of  the  super- 
posed magneto-machine  to  excite  the  electro-magnet  of 
the  lower  dynamo-machine,  there  is  established  in  the 
lower  machine  a  much  more  powerful  magnetic  field  than 
that  of  the  compound  permanent  magnet  of  the  upper 
machine,  and  from  the  lower  armature  a  current  of  much 
greater  power  than  that  induced  in  the  upper  armature 
is  obtained.  The  polarity  of  the  armature  is  reversed 
at  each  half-revolution,  and  the  alternately  opposite 


GENERATORS  OF  ELECTRICITY,  17 

currents  are  reduced  to  a  common  direction  by  means 
of  a  commutator  (Fig.  4). 


Fig.  4.  Commutator. 

The  calorific  effects  of  the  Wilde  machine,  whose  prin- 
ciple may  be  extended  indefinitely,  are  most  remarkable  ; 
but  it  should  be  borne  in  mind  that  in  no  machine  can 
the  electrical  energy  evolved  exceed  the  mechanical  force 
expended  in  producing  it. 

In  the  Wilde  machine  \ve  have  the  germ  of  a  perfect 
generator.  The  field  of  force  of  the  lower  armature  is 
created  and  sustained  by  an  invariable  exciting  current. 
Its  intensity,  therefore,  does  not  depend  upon  the  resist- 
ance of  the  external  working  circuit.  The  resistance  of 
the  armature-coils  may  be  a  tenth  or  less  of  the  resist- 
ance external  thereto,  so  that  ninety  per  cent,  or  more  of 
the  current  generated  in  the  machine  may  be  utilized 
in  the  production  of  light. 

Opposed  to  the  principle  of  Wilde  is  that  of  accumu- 
lation by  mutual  action,  in  which  the  currents  induced 
in  the  armature  are  made  to  circulate  through  the  coils 
of  the  electro-magnet  that  induced  them.  The  magnet- 
ism residual  in  the  iron  of  the  electro-magnet  induces  at 


18  ELECTRIC  LIGHTING  BY  INCANDESCENCE. 

first  a  weak  current  in  the  armature-coils,  and  this,  being 
returned  to  the  magnet-coils,  increases  the  power  of  the 
magnet,  and  induces  in  the  armature  a  correspondingly 
powerful  current,  which  is  again  returned  to  the  magnet- 
coils  ;  and  this  action  progresses  until  a  point  of  mag- 
netic saturation  is  attained.  The  principle  of  accumu- 
lation by  mutual  action  is  employed  in  the  Hafner- 
Alteneck,  the  Gramme,  Brush,  Hochhausen,  and  other 
generators  in  general  use  ;  and  where  a  single  lamp,  or  a 
limited  number  of  lamps,  is  to  be  operated,  it  does  not 
appear  advisable  to  employ  an  exciting  machine,  the 
practical  use  of  the  latter  being  in  the  lighting  of  build- 
ings or  sections  of  a  city  requiring  a  large  number  of 
lamps  and  a  common  source  of  supply. 

In  all  accumulative  machines  increase  of  resistance  in, 
or  interruption  of,  the  external  circuit  at  once  cuts 
down  or  destroys  the  field  of  force,  for  the  field  of  force 
is  dependent  entirely  upon  the  resistance  of  the  circuit, 
and  we  have  the  most  effective  work  when  the  resistance 
external  to  the  machine  is  sensibly  equal  to  its  internal 
resistance,  although  it  is  often  possible  to  obtain  satis- 
factory results  when  the  external  is  greatly  in  excess  of 
the  internal  resistance.  As  the  field  of  force  must  be 
created  by  the  charging-up  of  the  magnet  upon  its  own 
circuit,  it  is  clear  that  when  we  increase  the  external  re- 
sistance the  field  of  force  is  weakened,  and  very  soon  a 
point  is  reached  at  which  the  magnet  will  not  appre- 
ciably charge.  Thus  it  is  that  a  dynamo-machine  may 
successfully  operate  a  single  lamp,  or  a  limited  number 
of  lamps,  while  it  will  produce  no  good  effect  when  two  or 
a  greater  number  of  lamps  are  connected  in  circuit,  and 


GENERATORS  OF  ELECTRICITY. 


19 


in  order  to  obtain  the  best  results — /.  e. ,  the  maximum 
of  light  with  the  minimum  expenditure  of  power — sub- 
stantially fifty  per  cent,  of  the  current  generated  is  ordi- 
narily expended  in  exciting  the  machine,  and  fifty  per 
"cent,  in  the  production  of  light.  Compensating  for  in- 
creased resistance  in  the  external  circuit  by  increasing 
the  speed  of  the  generator  above  its  normal  velocity  is 
wasteful  of  power. 


Fig.  5.  The  De  Meriten*  Machine. 


The  permanent  field  magnet  of  the  earlier  machines 
lias  generally  given  way  to  the  more  compact  and  power- 
ful electro-magnet,  but  in  the  recent  invention  of  De 


20  ELECTRIC  LIGHTING  BY  INCANDESCENCE. 

Meritens  (Fig.  5)  the  original  form  of  magnet  is  revived. 
For  this  machine  great  efficiency  has  been  claimed  ;  and 
that  within  certain  limits  it  is  an  economical  generator 
of  electricity  we  have  no  reason  to  doubt.  The  saving 
of  the  power  expended  to  sustain  the  field  of  force  of 
dynamo-electric  machines  is,  of  course,  advantageous ; 
but  the  cost  of  construction,  multiplication  of  parts,  and 
cumbersomeness  of  large  generators  designed  upon  this 
plan  will  probably  operate  against  them,  as  they  have 
operated  against  the  similarly-designed  Alliance  and 
Holmes  machines.  In  construction  the  De  Meritens 
machine  consists  of  a  series  of  grooved  armatures,  like 
the  letter  H,  joined  side  by  side  and  mounted  upon  the 
periphery  of  a  diamagnetic  wheel,  so  as  to  constitute  an 
iron  ring  in  sections,  provided  with  as  many  projections 
as  there  are  distinct  pieces.  In  the  bottom  of  the 
grooves  the  armature  coils  are  wound ;  and  the  whole  is 
rotated  within  the  fields  of  force  of  a  series  of  powerful 
steel  magnets,  built  up  of  thin  plates  and  supported  in  a 
circular  frame.  The  methods  of  adjustment  of  parts 
employed  by  De  Meritens  are  simple  and  effective. 

The  Lontin  distributor  (Fig.  6)  is  one  of  several 
new  forms  of  generators,  embodying  the  principle  of 
Wilde,  designed  to  operate  a  considerable  number  of 
lamps  from  a  single  source.  The  exciting  machine  is 
of  the  dynamo-electric  type,  and  consists  of  an  elec- 
tro-magnet between  the  poles  of  which  revolve  a  num- 
ber of  radially-arranged  bar  electro-magnets  consti- 
tuting the  armatures.  The  current  produced  is  em- 
ployed in  sustaining  the  fields  of  force  of  the  distributor, 
which  consists  of  a  large,  stationary,  soft -iron  ring,  F,  to 


(JKNKRATORS  OF  ELECTRICITY. 


21 


which  are  secured  equidistantly  a  series  of  short  electro- 
magnets, B,  equal  in  number  to  the  electro-magnets,  M, 
of  the  inner  revolving  wheel.  The  revolving  magnets, 
which  are  connected  in  multiple  circuit,  are  charged 
by  the  exciting  machine  and  constitute  the  fields  of 
force.  As  the  ends  of  the  revolving  magnets  present 


Fig.  6.  Lontin's  Machine. 

alternately  opposite  poles  to  the  poles  of  the  stationary 
magnets,  alternating  currents  are  induced  in  the  latter, 
and  as  many  separate  lamps  may  be  worked,  from  a 
single  distributor  as  there  are  electro-magnets  B. 

Regarding  the  performance  of  the  Lontin  distributor, 
it  is  stated  that  in  the  small  machine  the  light  obtained 
per  horse-power  of  mechanical  force  expended  is  from 
400  to  600  candles,  while  in  a  larger  machine,  having  a 


22 


ELECTRIC  LIGHTING  BY  INCANDESCENCE. 


capacity  of  12  lights,  and  consuming  twelve  horse-power, 
the  light  obtained  per  horse-power  is  from  600  to  750 
candles.  A  generator  used  at  the  railway  station  at 
Lyons  fed  31  separate  lamps,  each  having  an  illuminat- 
ing power  of  340  candles,  but  the  value  of  the  mechani- 
cal energy  expended  is  not  known. 


Fig.  7.  The  Sawyer  Distributor. 


The  Sawyer  distributor  (Fig.  7)  bears  a  certain  resem- 
blance to  the  Lontin  machine,  but  is  based  upon  a  dif- 
ferent principle  of  action. 


GENERATORS  OP  ELECTRICITY. 


Fig.  8.  Magnet  and 
Armatures. 


It  is  a  well-known  fact  that  for  every  magnet  there 
is  a  point  of  maximum  sustaining  power.  Taxed  be- 
yond that  point,  the  magnet  will  no  longer  sustain  its 
armature.  Suppose  that  we  have  a  magnet,  N  S  (Fig.  8), 
whose  armature  or  armatures,  A,  re- 
quire all  its  power  to  sustain  them.  If, 
now,  we  bring  to  the  magnet  a  third 
armature,  B  (Fig.  9),  greater  in  mass 
than  either  of  the  armatures  A,  both 
armatures  A  will  fall  off,  because  arma- 
ture B,  of  greater  mass,  operates  to 
magnetically  short-circuit  them.  If  we 
have,  surrounding  armature  A,  a  coil  of 
insulated  wire,  when  we  approach  the 
magnet  with  armature  B  a  current  of  electricity  is  in- 
duced in  that  coil ;  and  when  we  move  armature  B  away, 
armature  A  being  within  the  mag- 
netic field,  a  current  of  opposite 
direction  is  induced  in  the  coil. 

In  the  Sawyer  distributor  both 
the  field  magnets  and  their  induc- 
tion armatures  are  stationary.  To 
the  inner  periphery  of  an  iron  ring 
are  fixed  a  series  of  electro-mag- 
nets whose  coils,  joined  together, 
are  fed  by  an  exciting  machine. 
Bolted  to  the  sides  of  the  polar 
extensions  of  the  magnets  by  means 
of  brass  screws,  and  prevented 

from  magnetic  contact  by  brass  plates,  C,  are  the  soft- 
iron  armatures  B,  whose  coils  are  connected  with  the 


N 


\ 


Fig.  9.  Magnet  with  unequal 
Armatures. 


24  ELECTRIC  LIGHTING  BY  INCANDESCENCE. 

lamps  to  be  operated.  A  soft-iron  armature,  D,  de- 
signed to  short-circuit  the  magnetic  force  of  the  field 
magnets,  is  rapidly  rotated,  its  projections  approaching 
almost  to  contact  with  the  polar  faces  of  the  field  mag^ 
nets.  The  cross-section  of  D  is  much  in  excess  of  the 
cross-section  of  B  ;  consequently,  when  the  former  is  in 
the  position  shown,  the  magnetic  force  is  almost  entire- 


rig.  10.  The  Seeley  Machine. 


ly  short-circuited  from  B.  As  the  position  of  the  pro- 
jections of  D  is  changed,  the  magnetic  force  of  the  field 
magnet  is  directed  through  the  armatures  B,  and  a  cur- 
rent of  electricity  of  one  direction  is  induced  in  their 
coils ;  as  the  projections  assume  the  position  shown  a 
current  of  the  opposite  direction  is  induced.  By  means 
of  this  generator  a  large  volume  of  electricity  is  obtain- 
able, but  in  effective  action  it  seems  to  be  inferior  to 
some  other  generators. 

The  Seeley  machine  (Fig.  10),  which  appeared  in 
the  year  1880,  contemplates  an  armature  entirely  of 
copper  wire  or  ribbon  (the  iron  core  being  discarded), 


GENERATORS  OF  ELECTRICITY. 


in  order  that  loss  of  power  consequent  upon  its  conver- 
sion into  heat,  and  the  injurious  effects  of  Foucault  cur- 
rents, may  be  avoided.  F  and  G  are  electro- 
magnets arranged  with  the  N"  pole  of  one 
magnet  opposite  to  the  S  pole  of  the  other. 
The  space  between  each  opposite  pair  of 
poles  is  from  one-fourth  of  an  inch  to  an 
inch,  and  in  this  narrow  space,  constituting 
a  concentrated  and  intense  magnetic  field, 
the  radial  wire  armatures  A  are  rotated.  The 
method  of  winding  the  armatures,  which  are  held  in 


Fig.  11.  Arma- 
ture of  See- 
ley  Machine. 


Fig.  12.  Siemens  Alternating  Current  Machine. 

place  by  a  central  clamping  device,  C  C,  fixed  to  shaft 
B,  and  an  outer  clamping-ring,  B,  is  shown  in  Fig.  11. 


26  ELECTRIC  LIGHTING  BY  INCANDESCENCE. 

The  shaft  of  the  machine  is  rotated  by  means  of  pulley 
E.  In  practice  there  are  six  magnets  on  each  side  of 
the  armature-disk,  and  twelve  armatures. 

A  form  of  alternating- current  machine,  the  same  in 
principle  as  the  Seeley  machine,  was  devised  by  Sie- 
mens and  Halske  in  1878,  and  consists  in  one  form  of 
a  central  disk  carrying  coreless  wire  helices  (Fig.  12). 
This  disk  is  rapidly  rotated  between  two  sets  of  electro- 
magnets whose  fields  of  force  are  sustained  by  a  small 
Siemens  continuous-current  machine. 


CHAPTER  II. 

GENERATORS   OF   THE  GRAMME  TYPE. 

AF  dynamo-electric  generators  none  are  better  known, 

or  more  extensively  employed,  than  those  of  M. 

Gramme,  whose  invention   has  excited  the  interest  of 

fche  scientific  world  since  its  first  presentation  to  the 


Fig.  13.  The  Gramme  Machine. 
27 


28  ELECTRIC  LIGHTING  BY  INCANDESCENCE. 

French  Academy  of  Sciences  in  1871.  The  essential  fea- 
ture of  the  Gramme  machine  (Fig.  13)  is  a  soft-iron  ring 
wound  throughout,  in  the  same  direction,  with  a  con- 
tinuous insulated  copper  wire,  the  terminals  of  which 
are  joined  together,  so  that  the  whole  constitutes  an 
endless  wire  helix  (Fig.  14). 


Fig.  14.  Principle  of  the  Gramme  Machine. 

In  order  to  arrive  at  an  understanding  of  its  opera- 
tion, let  us  suppose  that  the  wire  is  denuded  upon  the 
periphery  of  the  helix,  thus  forming  a  band,  composed 
of  bared  sections  of  the  wire,  running  around  the  outer 
circumference  of  the  ring.  In  this  we  have  one  element 
of  the  commutator,  the  other  of  which  is  composed  of 
the  collecting  brushes,  M  M',  which  make  connection 
with  the  bared  sections  of  the  helix.  When  the  ring  is 
placed  between  the  poles,  S  JS",  of  any  magnet,  the  ring 
constitutes  the  armature  of  that  magnet,  and  there  occur 
in  the  ring  two  consequent  poles,  S'  N'.  If  the  ring  is 
now  revolved  the  poles  developed  in  the  ring  remain  in- 
variably in  the  same  relation  with  respect  to  the  magnet 
poles,  N  S.  Whatever  may  be  the  rapidity  of  rotation, 
the  ring  poles,  W  S',  remain  fixed  in  space  and  each  part 


GENERATORS  OF  THE  GRAMME  TYPE. 


of  the  copper  lielix  successively  traverses  them.  It  is 
apparent,  therefore,  that  the  helix  will  be  the  seat  of  a 
current  of  one  direction  when  traversing  the  path  M  S  M', 
and  of  the  inverse  direction  when  traversing  the  path 
M'  N  M ;  and  the  part  of  the  helix  above  the  line  M  M' 
will  be  traversed  by  a  current  of  one  direction,  and  all 
parts  beneath  the  line  by  a  current  of  inverse  direction, 
precisely  as  in  the  case  of  two  galvanic  batteries,  each 
composed  of  an  equal  number  of  elements,  coupled  in 
multiple  or  opposition.  The  two  currents  are  equal  and 
opposite  and  balance  one  another. 

Generally  the  ring  is  made  of  iron  wire  (Fig.  15), 
and  in  practice  the  helix 
is  not  denuded  for  the 
purpose  of  establishing 
current-collecting  faces, 
but  is  divided  into  short 
coils  so  connected  as  to 
constitute  an  endless  coil 
wound  in  one  direction 
around  the  ring,  the  con- 


necting wires  between 
the  coils  being  connect- 
ed with  substantial  insulated  pieces  nearer  the  shaft, 
which,  together  with  the  collecting  brushes,  compose  the 
commutator.  In  the  Gramme  machine  there  are  no  sud- 
den reversals  of  polarity  in  the  ring,  but  a  continuous 
progressive  movement  of  the  consequent  poles,  which  are 
subject  to  displacement  in  respect  of  the  poles  of  the 
magnet  in  proportion  to  the  velocity  of  rotation  of  the 
ring. 


Fig.  15.    Armature  of  Gramme  Machine. 


30  ELECTRIC  LIGHTING  BY  INCANDESCENCE. 

To  produce  a  successful  Gramme  machine,  it  is  ne- 
cessary to  provide  the  magnet  with  polar  extensions 
overlapping  from  two-thirds  to  five-sixths  of  the  outer 
periphery  of  the  ring,  and  the  distance  between  the 
iron  of  the  ring  and  the  faces  of  the  polar  extensions 
presented  to  its  outer  periphery  should  in  no  case  ex- 
ceed one  and  a  half  inches,  and  in  small  machines 
should  not  exceed  one-half  inch.  The  helix  must  be 
wound  so  as  to  bring  the  layers  of  wire  within  this 
space,  and  the  polar  faces  should  be  in  as  close  proxi- 
mity to  the  outer  periphery  of  the  helix  as  may  be  com- 
patible with  safety  in  mechanical  construction. 

In  the  Gramme,  as  in  all  other  machines  provided  with 
iron  induction-cores,  the  heating  of  the  armature- 
coils  is  often  a  serious  defect,  especially  when  the  velo- 
city of  rotation  is  great  and  the  resistance  of  the  ex- 
ternal circuit  low ;  and  in  some  machines  the  heat  de- 
veloped is  so  great  as  frequently  to  be  destructive  of  the 
insulations.  Many  attempts  to  obviate  excessive  heat- 
ing have  been  made,  attended  with  a  greater  or  less  de- 
gree of  success,  the  most  common  of  which  is  by  increas- 
ing the  number  of  armatures  in  respect  of  the  number  of 
magnets,  as  in  multisectional  machines.  Another  method 
is  to  run  a  stream  of  water  through  the  shaft  of  the 
armature ;  or,  as  in  the  Hochhausen  electro-plating 
machine,  to  run  the  entire  armature  in  a  water-box,  the 
armature-helix  being  carefully  insulated  ;  or,  as  in  the 
Sawyer  machine,  to  cause  the  water  to  flow  throughout 
the  interior  mass  of  the  iron.  A  third  method  is  to  so 
construct  the  armature  as  to  subject  it  to  the  free  circu- 
lation of  currents  of  air. 


GENERATORS  OF  THE  GRAMME  TYPE.        3^ 

In  the  Maxim  machine  (Fig.  16),  the  last-described  me- 
thod is  employed.  This  generator,  which  has  recent- 
ly been  introduced  and  successfully  operated  in  New 
York  and  other  cities,  is  based  upon  the  Gramme 
principle  as  to  its  armature,  with  some  changes  in 


Fig.  16.  The  Maxim  Machine. 

the  construction  of  the  ring,  which  is  composed  of 
a  large  number  of  thin  flanges  of  soft  iron  arranged 
side  by  side  so  as  to  form  a  tube  or  hollow  cylinder 
of  considerable  length,  through  all  parts  of  which 
the  air  is  free  to  circulate.  The  electro-magnet  is  sim- 
ilar in  construction  to  the  compound  magnet  of  Dr. 


32  ELECTKIC  LIGHTING  BY  INCANDESCENCE. 

Siemens.  No  comparisons  of  the  efficiency  of  the 
Maxim  machine  with  other  generators  have  been  made  ; 
but  unless  the  resistance  of  the  external  circuit  is  low, 
the  armature  is  not  heated  so  highly  that  the  hand 
may  not  be  placed  upon  it. 

In  some  respects  similar  to  the  Gramme  is  the  Brush 
machine  (Fig.  17),  whose  extensive  employment  through- 
out the  United  States  has  demonstrated  its  efficiency  in 
the  production  of  a  series  of  voltaic  arcs.  The  Brush 
armature  consists  of  a  flat  ring  of  soft  cast-iron  revolv- 
ing in  its  own  plane.  This  ring  is  composed  of  two  or 
more  parts,  insulated  from  each  other,  and  each  provided 
with  a  series  of  grooves  designed  to '  prevent  the  induc- 
tion of  currents  in  the  iron  of  the  ring  itself,  and  to  con- 
fine the  action  of  the  field  of  force  to  the  generation  of 
currents  in  the  eight  helices  .with,  which  the  ring  is 
wound.  The  stationary  electro-magnets  face  both  sides 
of  the  armature  in  the  plane  of  its  rotation,  the  faces  of 
the  magnets  opposite  to  each  other  being  of  the  same 
polarity  ;  hence  the  soft-iron  ring  consists,  as  in  the 
Gramme  machine,  of  a  compound  semicircular  magnet 
whose  poles,  fixed  in  space,  are  constantly  changing  in 
respect  of  the  mass  of  the  ring.  In  the  arrangement  of 
the  armature-helices,  however,  the  Brush  machine  differs 
essentially  from  the  Gramme.  They  are  not  connected 
together  to  form  a  continuous  circuit,  but  each  pair  of 
diametrically  opposite  helices  is  connected  with  diame- 
trically opposite  segments  of  the  commutator,  which 
segments  are  not  connected  with  any  other  helices. 
Thus  each  pair  of  helices  is  entirely  independent  of  the 
others.  The  object  of  this  arrangement  is  to  remove 


GEXERATORS  OF  THE  GRAMME  TYPE.  33 


34  ELECTRIC  LIGHTING  BY  INCANDESCENCE. 

from  the  circuit  of  the  machine  that  pair  of  helices 
which,  at  the  neutral  point,  not  only  contributes  nothing 
in  useful  effect,  but  adds  to  the  internal  resistance  of  the 
machine.  Thus  in  the  Brush  machine  three-fourths  of 
the  armature-helices  only  are  included  in  the  circuit  at 
any  one  time. 

Various  sizes  of  the  Brush  generator  are  manufac- 
tured, the  sixteen-light  machine  being  employed  to  a 
considerable  extent  in  the  lighting  of  streets,  wharves,, 
hotels,  and  factories.  The  resistance  of  the  useful  ar- 
mature-coils is  from  four  to  six  ohms,  and  the  resistance 
of  the  magnet-coils  from  six  to  eight  ohms,  making  the 
total  internal  resistance  of  a  sixteen-light  machine  from 
ten  to  fourteen  ohms.  The  resistance  of  the  external  cir- 
cuit is  the  sum  of  the  resistance  of  all  the  lamps,  the  in- 
ternal resistance  of  each  of  which  varies  from  one  to 
five  ohms.  It  is  stated  by  the  manufacturers  that  the 
sixteen-light  machine  (the  diameter  of  whose  armature  is 
twenty  inches,  and  length  of  base  sixty-eight  inches), 
driven  at  a  speed  of  750  revolutions  per  minute,  absorbs 
about  one  horse-power  per  lamp.  In  his  statement  of  the 
efficiency  of  his  system,  Mr.  Brush  says  that  as  many  as 
33  lamps  have  been  operated  simultaneously  in  the  cir- 
cuit of  this  machine  at  a  speed  of  800  revolutions,  with 
an  arc  of  appreciable  length  in  each  lamp ;  but  the  total 
light  produced  was  less  than  half  that  obtained  when 
sixteen  or  seventeen  lamps  were  employed. 

The  investigations  of  the  Franklin  Institute  as  to  the 
relative  efficiency  of  the  Gramme  and  Brush  machines 
(1877-78),  in  maintaining  the  voltaic  arc,  resulted  in  the 
following  determinations  : 


GENERATORS  OF  THE  GRAMME  TYPE.        35 

"The  Gramme  machine  is  the  most  economical,  con- 
sidered as  a  means  for  converting  motive  power  into  elec- 
trical current,  giving  in  the  arc  a  useful  result  equal  to 
38  per  cent.,  or  to  41  per  cent,  after  deducting  friction 
and  the  resistance  of  the  air.  In  this  machine  the  loss  of 
power  in  friction  and  local  action  is  the  least.  The  large 
Brush  machine  comes  next  in  order  of  efficiency,  giving 
in  the  arc  a  useful  effect  equal  to  31  per  cent,  of  the  total 
power  used,  or  37|-  per  cent,  after  deducting  friction." 

As  the  result  of  the  Franklin  Institute  experiments  it 
was  shown  that  the  Brush  machine,  at  a  speed  of  1,340 
revolutions  per  minute  and  consuming  3.26  horse-power, 
developed  a  light  of  1,230  standard  candles,  or  377  can- 
dles per  horse-power  ;  while  the  Gramme  machine,  run  at 
a  speed  of  800  revolutions  and  consuming  1.84  horse- 
power, produced  a  light  of  705  candles,  or  383  candles  per 
horse-power.  In  running  25  minutes  the  Brush  machine 
increased  in  temperature  from  73£°  to  88°  Fahr.  The 
internal  resistance  of  the  machine  was  .483  of  an  ohm, 
and  the  resistance  of  the  lamp  .54  of  an  ohm.  The  in- 
ternal resistance  of  the  Gramme  machine  was  1.669  ohms, 
and  the  resistance  of  the  arc  1.87  ohms. 

Underlying  the  principle  of  the  Gramme  generator, 
Ibut  coming  to  general  notice  subsequent  to  the  inven- 
tion of  Gramme,  is  the  Pacinotti  ring  machine,  de- 
vised by  Dr.  Antonio  Pacinotti  in  1860,  and  described  in 
the  June  number  of  the  Italian  scientific  journal,  II 
Nuow  Cimento,  four  years  later.  The  Pacinotti  ma- 
chine (Fig.  18)  was  the  first  machine  to  produce  a  current 
of  electricity  continuous  in  character  and  constant  in 
direction  and  intensity  ;  and  it  differs  from  the  Gramme 


36  ELECTRIC  LIGHTING  BY  INCANDESCENCE. 

in  principle  solely  in  that  the  revolving  ring  is  pro- 
vided with  projections,  as  in  the  Brush  machine, 
between  which  the  endless  helix  is  wound.  Although 
the  design  of  Pacinotti  was  to  produce  an  electro-mag- 
netic engine,  he  clearly  described  its  conversion  into  a 
generator  capable  of  producing,  in  combination  with  a 


PHOTO.ENC.CO.  H.Y. 

Fig.  18.  The  Pacinotti  Ring  Machine. 


permanent  or  an  electro  magnet,  a  continuous  current 
of  constant  direction.  The  chief  improvement  of  Gramme 
consisted  in  omitting  the  projections  upon  the  ring,  and 
covering  the  entire  mass  of  iron  with  the  wire  helix  ; 
but  the  percentage  of  gain  from  this  change  in  con- 
struction is  not  known.  In  general  construction,  how- 
ever, the  Gramme  generator  is  new,  and  superior  to  the 
Pacinotti  ring  machine. 


CHAPTER  III. 

GENERATORS   OF  THE   NEW   SIEMENS   TYPE. 

"FOLLOWING  the  generator  of  M.  Gramme  comes  the? 

equally  remarkable  invention  of  v.  Hafner-Alteneck 

(Fig.  19),  generally  known  as  the  New  Siemens  machine, 

the  compound  electro-magnet  of  which  has  the  flat  shape 


Fig.  19.  The  New  Siemens  Machine. 

of  the  magnet  of  the  Wilde  machine.     In  this  generator 
the  armature  consists  of  a  long,  soft-iron,  hollow  drum 


37 


38  ELECTRIC  LIGHTING  BY  INCANDESCENCE. 

rotating  between  the  curved  polar  faces  A  of  the  electro- 
magnet B.  This  drum  is  wound  longitudinally,  and  in  a 
peculiar  manner,  with  insulated  wire,  covering  all  parts 
of  the  same,  and  connected,  at  different  points,  with  the 
insulated  commutator  segments,  in  such  a  manner  that 
the  coil  is  a  continuous  one,  endless  as  in  the  Gramme 
machine,  but  not  wound  or  connected  in  the  same  man- 
ner. When  the  armature  is  caused  to  rotate,  a  current 
is  induced  in  the  armature- coils,  and  the  magnet  is  ex- 
cited, upon  the  principle  of  mutual  action  already  de- 
scribed. 

The  smallest-sized  Hafner-Alteneck  machine  is  698mm 
in  length,  572mm  wide,  and  233mm  high  ;  the  drum  is 
388mm  long,  and  carries  28  wire  coils  and  a  commutator 
divided  into  56  parts.  Its  weight  amounts  to  115  kilo- 
grammes ;  the  maximum  velocity  of  the  drum,  900  re- 
volutions per  minute  ;  and  the  intensity  of  the  light  pro- 
duced, 1,400  standard  candles.  One  and  a  half  horse- 
power is  required  to  run  it.  The  medium-sized  ma- 
chine differs  in  construction  but  slightly  from  the  above. 
It  is  757mm  in  length,  700mm  wide,  and  284mm  high  ;  the 
drum  has  a  length  of  456mm,  and  is  also  wound  with  28 
coils.  The  commutator  is,  therefore,  also  composed  of 
56  pieces,  upon  which  wire  collecting  brushes  are  made 
to  press.  The  machine  weighs  200  kilogrammes,  and 
produces,  at  its  maximum  velocity  of  700  revolutions 
per  minute,  a  light  of  4,000  candles,  and  absorbs  three 
and  one-half  horse-power. 

In  the  South  Foreland  lighthouse  experiments,  con- 
ducted by  Prof.  Tyndall,  the  relative  efficiency  of  the 
Gramme  and  the  Hafner-Alteneck  machines  was  made 


GENERATORS  OF  THE  NEW  SIEMENS  TYPE.  39 

the  subject  of  special  investigation.  It  was  found  that 
at  a  speed  of  420  revolutions  per  minute,  absorbing  5.3 
horse-power,  the  Gramme  machine  developed  a  light  of 
758  candles  per  horse-power.  The  largest  Hafner-Alte- 
neck  machine,  at  480  revolutions  and  absorbing  9. 8  horse- 
power, developed  911  candles-light  per  horse-power; 
while  a  smaller  machine,  at  850  revolutions  per  minute, 
absorbing  3.5  horse-power,  developed  954  candles-light 
per  horse-power.  A  second  small  machine  developed 
for  a  brief  period  1,254  candles-light  per  horse-power. 
In  another  form  of  the  New  Siemens  machine  (Fig.  20), 


Fig.  20.  New  Siemens  Machine,  Stationary  Armature-Core. 

the  iron  armature  core  is  stationary,  and  the  coils  of 
wire  are  fixed  upon  and  rotate  with  a  cylinder  of  Ger- 
man silver  surrounding,  but  not  touching,  the  core.  In 
Dr.  Schellen's  description  of  this  form  of  generator, 
which  is  most  complete,  he  illustrates  the  fact  that  when 
the  armature-core  moves  in  a  magnetic  field,  such  motion 
develops  induced,  or  so-called  Foucault,  currents,  which, 
if  not  conducted  away,  become  transformed  into  heat, 
and  thus,  according  to  the  circumstances  of  the  case,  give 


40  ELECTRIC  LIGHTING  BY  INCANDESCENCE. 

rise  to  a  considerable  heating  of  the  metallic  bodies  in 
motion.  As  long,  therefore,  as  the  iron  core  revolves 
with  the  coiled  drum  through  the  magnetic  iield,  these 
currents  are  not  to  be  avoided,  though  they  may  be  di- 
minished to  some  extent  by  constructing  the  armature 
of  coils  of  iron  wire  instead  of  massive  iron.  It  was, 
therefore,  determined  to  secure  the  iron  armature  inside 
the  drum,  and  so  prevent  it  from  taking  part  in  the  mo- 
tion of  the  latter.  As  a  matter  of  course,  this  renders 
the  construction  of  the  drum  much  more  complicated, 
especially  when  it  is  considered  that  the  long  drum, 
with  its  surrounding  coils  of  wire,  has  to  be  moved 
through  the  narrowest  possible  space  between  the  polar 
faces  of  the  electro-magnet  and  the  stationary  iron  core. 
In  the  engraving,  which  is  composed  from  Dr.  Schel- 
len's  work,  we  have  a  horizontal  section  of  the  machine, 
showing  the  thin  German-silver  drum  upon  which  the 
wire  is  wound.  Each  terminal  face  of  the  drum  carries 
a  short  tube,  which  tubes  form  the  trunnions  of  the 
drum  and  lie  in  boxes  provided  with  oil-cups.  An  iron 
shaft,  secured  by  means  of  screws  in  its  supporting  pil- 
lars, passes  through  these  tubes  into  the  interior  of  the 
iron  armature,  where,  by  means  of  two  disks  bolted  to 
each  other,  the  armature  is  fastened  to  the  shaft.  The 
drum  is  surrounded  on  the  outside,  at  two  opposite 
places,  for  about  two-thirds  of  its  circumference  and 
over  its  entire  length,  by  the  two  curved  polar  faces  of 
the  magnet.  These  are  placed  as  closely  as  possible  to 
the  wire  surrounding  the  German-silver  drum,  and  form, 
with  the  stationary  hollow  iron  interior  core,  a  narrow 
annular  space,  constituting  the  magnetic  field,  through 


GENERATORS  OF  THE  NEW  SIEMENS  TYPE.  41 

which  the  drum,  with  its  surrounding  wires,  must  pass 
in  rotation  with  the  utmost  possible  freedom.  For  seve- 
ral reasons  this  form  of  the  New  Siemens  machine  has 
tailed  to  yield  results  sufficiently  satisfactory  to  war- 
rant its  manufacture  in  place  of  the  simpler  form  in 
which  the  iron  cylinder  rotates  with  the  surrounding 
coils. 

The  defect  of  the  Hafner- Alteneck  machine,  as  was  the 
case  with  the  Wilde  machine,  is  found  in  excessive  heat- 
ing of  the  armature,  and  this  is  frequently  so  great  as  to 
destroy  the  insulations.  Indeed,  injurious  heating  is  the 
defect  of  nearly  all  generators,  for  the  local  action  of 
dynamo-machines  is  analogous  to  the  local  action  of 
galvanic  batteries,  and  the  temperature  must  continually 
increase  until  the  loss  by  radiation  and  convection  equals 
the  amount  of  heat  produced.  If  a  machine,  through 
running,  acquires  a  high  temperature  with  a  proper  ex- 
ternal resistance,  its  efficiency  is  low,  and  any  heating 
whatever  reduces  its  efficiency.  Thus  the  large  Brush 
machine  at  the  Franklin  Institute,  in  running  25  minutes, 
increased  in  temperature  from  73£°  to  88°  Fahr. ,  and  in 
its  internal  resistance  from  .483  to  .493  ohm.  In  ma- 
chines of  the  Hafner- Alteneck  type  the  heat  produced  is 
much  more  marked  and  injurious,  and  the  various  im- 
provements upon  or  modifications  of  the  same,  as  in 
the  Hochhausen,  Thomson  and  Houston,  Weston,  Edi- 
son, and  the  Sawyer  generators,  have  in  view  the  ob- 
viation  of  this  evil. 

The  Edison  Machine  (Fig.  21)  has  recently  attracted 
much  attention.  The  compound  electro-magnet  of  Sie- 
mens is  replaced  by  a  long  and  powerful  simple  electro- 


42  ELECTRIC  LIGHTING  BY  INCANDESCENCE. 

magnet,  and  in  constructing  the  armature  the  hollow 
drum  is  modified.     In  efficiency  the  Edison  generator, 


Fig.  21.  The  Edison  Machine. 

properly  constructed,  would  seem  to  be  equal  to  any 
of  the  Hafner-Alteneck  form,  although  we  have  no  data 
upon  which  to  base  a  conclusion.  The  armature  is 


GENERATORS  OF  THE  NEW  SIEMENS  TYPE. 


constructed  in  two  ways.  In  the  first,  of  which  Fig.  22 
is  a  sectional  end  view,  a  helix  of  iron  wire,  wound  like 
thread  upon  a  spool,  surrounds  a  wooden 
or  other  diamagnetic  roll.  This  helix  con- 
stitutes the  core  of  the  armature.  Over  it 
the  insulated  coils  are  wound  as  shown  in 

Fig.  23.  Fig.    22.      Sectional 

-r      .-,  -.    «  „  -r.  -..  End  View  of  Arma- 

In  the  second  form  of  Edison  armature,    ture. 
it  is  composed  of  a  large  number  of  thin,  soft-iron  flanges, 
similar  to  those  used  in  the  Maxim  machine,  and  a  free 
circulation  of  currents  of  air, 
to  avoid  destructive  heating,  is 
provided. 

In  the  Sawyer  machine,  of 
which  Fig.  24  is  an  illustration, 
the  compound  magnet  of  Sie- 
mens is  discarded,  and  a  simple  Wilde  electro-magnet  of 
cast-iron  is  substituted  therefor.     To  secure  the  maxi- 
mum   of   magnetic    power,   the 
limbs  of  the  magnet  increase  in 
thickness  as  they  approach  the 
base  (Fig.    25).      To  the  upper 
ends  of  the  magnet  limbs  cast- 
iron  polar  extensions  are  bolted. 

The  generator  shown  in  the  il- 
lustration is  the  smallest  size  of 
machine,  the  armature  being  2 

inches    in  diameter,  and,  as  in      Fig  ^  End  view  of  Magnet< 
other  similar  machines  of  small 

size,  the  armature-core  consists  of  a  substantially  solid 
roll  of  malleable  iron.     In  large  machines  the  armature, 


o    o 


0     O 


GENERATORS  OF  THE  NEW  SIEMENS  TYPE.  45 

like  that  of  the  Hafner-Alteneck  machine,  is  in  the  form 
of  a  hollow  drum. 

To  prevent  heating,  the  malleable  iron  roll  is  con- 
structed as  shown  in  the  sectional  end  and  side  views, 
Fig.  26.  Around  a  series  of  wrought-iron  tubes,  B,  the 


J?. 

Fig.  26.  Construction  of  Armature-Core. 

iron  A  is  cast,  and  over  the  ends  are  secured  malleable 
iron  caps,  D.  The  shaft  C  is  hollowed  out  a  portion  of 
its  length  from  each  end,  and  provided  with  openings 
into  the  spaces  enclosed  by  caps  D.  All  the  joints  are 
water-tight.  By  means  of  a  closely-fitting,  though  loose, 
entrance-pipe,  a  small  stream  of  water  is  let  into  one  end 
of  the  shaft  and  passes  in  the  direction  of  the  arrow  into 
the  cap  space,  thence  through  tubes  B,  and  outwardly 
through  the  opposite  cap  space,  the  hollowed  shaft,  and 
a  closely-fitting  waste-pipe. 

The  armature  of  the  larger  machines  is  illustrated  in 
Figs.  27  and  28.  Upon  the  shaft  A  is  fixed  a  brass 
cylinder,  B,  which  is  water-tight  as  to  the  inner  cham- 
ber. Over  this  cylinder,  and  leaving  a  space  between,  is 
fixed  the  iron  drum  D,  whose  caps,  C,  are  keyed  to  the 
shaft.  In  the  annular  space  thus  formed  between  cylin- 
der B  and  drum  D  the  water  circulates. 


46 


ELECTRIC  LIGHTING  BY  INCANDESCENCE. 


In  principle  the  same  as 
the  Hafner-Alteneck  ma- 
chine, it  is  not  surprising 
that  this  generator  should 
have  yielded  as  good  re- 
sults ;  but  the  temperatures 
maintained  while  doing 
work  have  been  of  an  un- 
expected character.  In  in- 
ternal resistance  the  ma- 
chine varies  from  .25  of  an 
ohm  to  5.  ohms,  according 
to  the  work  to  be  done  ; 
and  the  distance  between 
the  periphery  of  the  iron  of 
the  armature  and  the  polar 
faces  of  the  magnet  is  from 
five-sixteenths  of  an  inch  to 
one  and  one-  eighth  inches, 
according  to  the  size  of  the 
machine.  Each  polar  face 
covers  one-third  of  the  peri- 
phery of  the  armature  when 
wound  with  the  induction 
helices. 

The  No.  1,  or  smallest 
size  of  machine,  driven  at  a 
speed  of  1,000  revolutions 
per  minute  by  a  belt  one 
inch  in  width,  yields  a  light 


gide  Section  of  Large  Armature 


by  the  voltaic  arc  of  500  candles,  and  by  incandescence 


GENERATORS  OF  THE  NEW  SIEMENS  TYPE. 


47 


275  candles.  No  deduction  is  made  for  the  element 
of  friction,  the  percentage  of  which  in  small  machines 
is  large. 


Fig.  28.  End  Section  of  Large  Armature. 


The  following  table,  compiled  from  a  series  of  tests 
made  in  November,  1880,  shows  the  average  temperatures 
observed  at  the  beginning  and  'end  of  three  hours'  run- 
ning, operating  a  closed  circuit : 


No.  of 
machine. 

Internal    re- 
sistance  of 
machine,   in 
ohms. 

External  re-       Temperature 
sistance          of   machine   at 
of  circuit,  in       beginning  of 
ohms.           run,  in  degrees 

Temperature 
of  armature  at 
end  of  run, 
in  degrees  Fahr. 

Temperature 
of  magnet-coils 
at  end  of  run,  in 
degrees   Fahr. 

Fahr. 

I 

•25 

•25 

80° 

7i° 

84° 

2 

I-I5 

•75 

76° 

73°                   82° 

3 

1-5 

1-5                      7Q° 

54°                   84-° 

3 

1-5                    .75                  79° 

65° 

85° 

Reduction  of  the  temperature  of  the  armature  below 
that  of  the  surrounding  air  was  so  entirely  unexpected 
that  on  November  22  a  prolonged  test  of  the  No.  2  ma- 
chine, wound  with  a  different  size  of  wire,  was  made. 
The  internal  resistance  of  the  machine  was  found  to  be 


48 


ELECTRIC  LIGHTING  BY  INCANDESCENCE. 


1.27  ohms,  and  the  resistance  of  the  external  circuit  .9; 
ohm,  making  the  total  resistance  2.17  ohms.  The  dura- 
tion of  the  test  was  from  9.30  A.M.  until  9  P.M.  Obser- 
vations were  carefully  made  both  at  the  beginning  and 
end  of  the  run,  and  at  intermediate  intervals,  with  the 
following  result : 


Temperature 
of  machine 
at  start. 

Average  tem- 
perature of 
laboratory. 

Average 
temperature 
of  water  be- 
fore entering 
armature. 

Average 
temperature  of 
water  on 
leaving  arma- 
ture. 

Average  tem- 
perature  of 
armature. 

Average 
temperature 
of 
magnet-coils 

73°  F. 

73^°  F. 

58°  F. 

67°  F. 

67i°  F. 

76°  F. 

In  every  case  the  temperature  of  the  armature  is  found 
to  decrease,  although  the  larger  sizes  of  machines  have 
not  been  subjected  to  thermometric  measurement. 

There  is  some  diversity  of  opinion  regarding  the  best 
method  of  winding  the  Haf  ner-Alteneck  armature.  Very 


Fig.  29.  Method  of  Winding  Armature. 

little  is  generally  known  about  the  subject,  except  that 
there  are  several  methods,  none  of  which  have  ever  been 
made  very  clear.  A  method  of  winding,  substantially  as 
good  as  any,  and  one  that  has  been  used  in  both  the  Edi- 
son and  the  Sawyer  machines,  is  illustrated  in  Fig.  29. 


GENERATORS  OP  THE  NEW  SIEMENS  TYPE. 


49 


The  armature  is  divided  into,  say,  28  equal  sections, 
and  the  requisite  number  of  convolutions  of  the  wire,  al- 
ways the  same,  is  wound  in  14  separate  coils  longitudi- 
nally around  the  drum,  closely  together,  and  with  the 


2* 


*—3 


-2 


Fig  30.  Connections  of  Armature-Coils. 

ends  left  free,  in  the  manner  shown.  The  coil  No.  2  fol- 
lows coil  No.  1,  and  coil  No.  3  follows  coil  No.  2,  and 
so  on  until  the  28  sections  (14  on  each  half  of  the  drum) 
are  filled,  the  -f-  sign  representing  the  starting  end  and 
the  —  sign  the  termination  of  the  wire  composing  each 


50  ELECTRIC  LIGHTING  BY  INCANDESCENCE. 

coil.  Covering  of  the  drum  with  asbestos-paper  to  en- 
sure proper  insulation  is  advisable,  and  in  order  to  facili- 
tate the  winding  it  is  useful  to  insert  temporary  guiding- 
pins  at  the  ends  and  middle  of  the  drum,  on  the  lines 
dividing  the  sections.  Accurate  laying  of  the  wire  is 


7+*  + 


Fig.  31.  Superposed  Coils  and  Connections. 

essential.  After  winding,  the  coils  are  bound  to  the 
drum  by  fine  brass  wires  wound  so  as  to  form  a  band 
around  it,  and  soldered.  There  should  be  several 
such  bands  at  different  points  along  the  length  of  the 


GENERATORS  OF  THE  NEW  SIEMENS  TYPE. 


51 


drum,  protected  from  contact  with  the  wire  of  the  coils 
by  interposed  bands  of  mica.  To  the  free  ends  of  the 
coils,  through  a  sleeve  on  the  shaft  of  the  machine,  the 
fourteen  commutator  segments  are  connected  as  shown 
in  Fig.  30,  in  which  A  is  the  shaft,  B  insulating  disk, 
C  C  commutator  segments,  and  D  D  collecting  brushes. 

In  some  cases  it  is  preferable  to  superpose  coil  No.  2 
upon  coil  No.  1,  etc.,  as  shown  in  Fig.  31,  in  which  case 
the  drum  is  divided  into  fourteen  sections.  The  connec- 
tions of  the  commutator  segments,  as  will  be  seen,  re- 
main the  same. 

The  collecting  brushes  bear  seriatim  upon  commutator 
segments  1,  8 ;  2,  9  ;  3,  10  ;  4,  11  ;  5,  12 ;  6,  13  ;  7,  14 ;  8, 
1  ;  9,  2  ;  10,  3 ;  11,  4  ;  12,  5  ;  13,  6 ;  14,  7 ;  and  in  each 
of  the  respective  positions  the  circuit  of  the  armature- 
coils,  the  sections  of  which  now  constitute  a  continuous^ 
endless  conductor,  is  as  shown  on  page  52 : 


IS     9 


Fig.  32.  Ilcrr  Frolich  Winding. 


Fig.  33.  Brfegu6t  Winding. 


Generally,  it  is  advisable  to  divide  the  armature-coil 
into  as  many  sections  as  may  be  consistent  with  the 
practical  mechanical  construction  of  the  armature  and 
commutator,  in  order  that  the  coil  may  cut  the  lines  of 


ELECTRIC  LIGHTING  BY  INCANDESCENCE. 


magnetic  force  the  greatest  possible  number  of  times  in 
a  single  revolution  of  the  armature. 


Segment  of 
commutator      in 
contact  with  ist 
brush. 

Direction  and  division  of  the  multiple  circuit  from  brush 
to  brush. 

Segment  of 
commutator     in 
contact  with  ad 
brush. 

I 

(    1  +  14  —  ii  —  ID—    7—   6  —    3—  ) 
1    4  —    5—    8—   9—12  —  13—    2~|-   f 

8 

2 

(    4+    1  +  14—  ii  —  10—    7—   6—   ) 
(5—8—   9—12  —  13—    2  +    3+   f 

9 

3 

(    5  +   4+    1  +  14—  ii  —  10—    7—   ) 
•j    8—    9—12-13-    2+    3+    6+   f 

10 

4 

(    8+    5+    4+    1  +  14—  ii  —  10—   ) 
1    9  —  12  —  13—    2+    3-f-   6+    7+   } 

ii 

5 

j    9+    8+    5  +   4+    1  +  14—  ii—   ( 
(12  —  13—    2  +    3+    6+    7+10  +   f 

12 

6 

JI2  +    9+    8+    54-    4+    1  +  14-   J. 
(13—    2-j-    3-|-    6-j-    7  +  io+ii  +   f 

13 

7 

(13  +  12+    9+    8+    5+   4+    i  +   j. 
\    2+    3+    6+    7  +  10+11  +  14+   f 

14 

8 

(    2_I3  +  I2+    9+    8+    5+   4+   I 
1    3+   6+    7  +  10+11  +  14+    i-  J 

I 

9 

j    3—    2  —  13  +  12+    9+    8+    5+i 
{    6+    7  +  10+11+14+    i-   4-  f 

2 

10 

(    6-    3-    2-13  +  12+    9+    8+   ) 
/    7  +  10+11  +  14+    i—   4—    5—   f 

3 

ii 

j    7—   6—    3—    2—13  +  12+    9+   ) 
(10+11  +  14+    i—    4—    5—    8—   f 

4 

12 

j  10—    7—   6—    3—    2  —  13+12+   ) 
(11  +  14+    i—   4—    5—    8—   9—   f 

5 

13 

jn  —  10—    7—    6—    3—    2  —  13+    ( 
(14+    i—    4—    5—    8—    9  —  12—   f 

6 

14 

(14  —  ii  —  10  —    7  —    6  —    3  —    2  —   ( 
(    i—   4—    5—    8—    9—12  —  13—   f 

7 

The  method  of  winding  the  armature  devised  by  Herr 
Frolich  (Fig.  32)  comprises  sixteen  vertical  conductors 
arranged  in  pairs  at  the  point  of  a  regular  octagon,  and 
crossing  the  octagon  by  the  diagonals  at  one  end  of  the 
armature,  and  by  long  chords,  crossing  in  the  form  of  an 


GENERATORS  OF  THE  NEW  SIEMENS  TYPE.  53 

eight-pointed  star,  at  the  other.  In  the  method  dis- 
covered by  M.  Breguet  (Fig.  33),  the  portions  of  the 
coils  which  cross  the  ends  of  the  armature  to  unite 
the  sixteen  vertical  wires  cross  the  octagon  along  short 
chords. 


CHAPTER  IY. 

INCANDESCENT   LAMPS. 

PRODUCING  light  by  heating  a  poor  conductor  of 
electricity  to  incandescence  is  a  favorite  conception 
of  experimentalists,  and  numerous  attempts  have  been 
made  toward  its  practical  realization.  In  nearly  every 
instance  these  attempts  have  resulted  in  failure,  not  so 
much  because  of  any  inherent  defect  of  principle  as  be- 
cause of  imperfections  in  the  details  of  construction  and 
operation. 

Lighting  by  incandescence  involves  a  principle  as  sim- 
ple as  lighting  by  the  voltaic  arc.  The  conductor  ren- 
dered luminous  is  of  poor  conductivity,  or,  in  other 
terms,  of  high  resistance.  The  resistance  of  the  wires 
connecting  it  with  the  generator  of  electricity  may  be 
disregarded.  Therefore  the  current  generated  is  divided 
between  the  generator  and  the  poor  conductor  exactly 
in  proportion  to  their  respective  resistances  ;  and  as  the 
latter  is  contained  in  small  compass,  the  current  is  con- 
centrated at  a  small  point  and  there  produces  calorific- 
effects  sufficient  to  yield  light. 


INCANDESCENT  LAMPS.  55 

When  a  body  is  at  the  temperature  of  1,000°  C.  we 
have  the  heat-rays : 

At  1,200°  we  have  the  orange  rays. 
"  1,300°    "     "        "  yellow  rays. 
"  1,500°    "     "        "  blue  rays. 
"  1,700°    "     "        "  indigo  rays. 
«  2)000°    u     «        «  Vi0iet  rays. 

Above  2,000°  C.  we  have  all  the  rays  of  the  sun.  In 
incandescent  carbon  lighting  the  conductor  is  raised  to  a 
temperature  much  in  excess  of  2,000°. 

Many  conductors  may  be  employed  in  the  production 
of  light  by  incandescence  ;  and  it  is  a  curious  fact  that 
experimentalists  have  almost  invariably  followed  a  beat- 
en course,  passing  from  one  metal  to  another :  from  pla- 
tinum to  iridium  and  iridio-platinum ;  from  the  metals 
to  carbon-coated  and  intermixed  asbestos  and  other  re- 
fractory materials  ;  and  finally  to  carbon  alone.  As 
carbon,  pure  and  simple,  has  been  clearly  determined  to 
be  the  only  suitable  substance,  we  shall  leave  out  of  con- 
sideration all  other  conductors  of  electricity. 

There  are  two  types  of  incandescent  lamps  in  use, 
those  which  burn  in  the  air  and  those  in  which  the  lu- 
minous conductor  is  enclosed  in  a  globe  exhausted  of 
air  or  containing  an  atmosphere  of  nitrogen  or  other  gas 
for  which  carbon  at  high  temperatures  has  no  chemical 
affinity.  The  open-air  lamp  is  subject  to  so  many  ob- 
jections that  it  is  doubtful  whether  it  will  ever  be 
successfully  employed  ;  but  the  efforts  of  Eenier  and 
Werdermann  have  done  much  towards  reducing  it  to 
practical  form.  The  Renier  lamp  (Fig.  34)  consists  of  a 
long  pencil  of  carbon  continuously  fed  between  an  elas- 


ELECTRIC  LIGHTING  BY  INCANDESCENCE. 


tic  contact  to  a  bearing  upon  a  carbon  roller  at  a  point 
between  the  vertical  and  the  horizontal.  The  upper  or 
elastic  contact  compresses  the  pen- 
cil laterally,  and  one  terminal  of 
the  conducting  wire  is  connected 
with  this  contact.  The  other  ter- 
minal is  connected  with  the  carbon 
roller.  The  pencil,  being  consumed 
at  the  lower  extremity  more  rapid- 
ly than  at  any  other  place,  di- 
minishes in  length,  and  this  di- 
minution is  compensated  by  the 
continuous  downward  feeding  of 
the  pencil.  Rotation  of  the  car- 
bon roller  to  carry  away  dead 
fragments  of  carbon  is  obtained 
from  the  tangential  component  of 
the  pressure  of  the  pencil  on  the 
periphery  of  the  roller. 

The  Werdermann  lamp  (Fig.  35) 
is  the  reverse  of  the  Renier  lamp 
in  construction  and  operation.  In 
this  lamp  the  carbon  pencil  is  fed 
upward,  through  an  elastic  con- 
tact, by  means  of  a  weight  or 
spring,  against  a  solid  stationary 
block  of  carbon. 

Both  the  Renier  and  the  Wer- 

Fig.  34.  Remer's  Lamp. 

dermann  lamps,  under  proper  con- 
ditions, should  yield  a  higher  percentage  of  light  per 
horse-power  than  lamps  in  which  the  carbon  is  protected 


INCANDESCENT  LAMPS.  57 

from  oxygen ;  but  in  both  these  lamps  the  constant  re- 
newal of  the  carbon  pencil  and  points  of  contact  neces- 
sary are  objections  to  be  surmounted. 

The  earliest  attempt  to  isolate  an  incandescent  carbon 
conductor  from  oxygen  appears  to  have  been  made  by 


Fig.  35.  The  Werdermann  Lamp. 

Starr  in  the  year  1845  ;  *  and  it  is  a  matter  of  some  sur- 
prise that  this  patient  investigator,  whose  conception 
included  the  entire  range  of  divisibility  of  the  light, 
should  have  stopped  but  little  short  of  realizing  a  prac- 
ticable system  of  lighting.  The  Starr-King  burner  (Fig. 

*  Starr- King  ;  English  patent  No.  10,919,  1845. 


58  ELECTRIC  LIGHTING  BY  INCANDESCENCE. 

36)  consists  of  a  conducting  wire,  D,  sealed  in  the  glass 
of  a  Toricellian  vacuum-tube,  and  connecting  with  a  car- 
bon rod,  A,  whose  lower  extremity  is  in  contact  with  a 
second  conductor  resting  in  the  quicksilver.  The  bar 
B,  of  porcelain,  serves  as  a  support  for  the  apparatus. 
For  several  reasons  this  lamp  could  not  have  been  a 
successful  one,  as  will  be  made  clear  in  another  chapter.* 
In  1873,  nearly  thirty  years  later,  came  the  invention 
of  Lodyguine,f  a  Russian  physicist,  who  was  awarded, 
during  the  subsequent  year,  the  great  prize  of  the  St. 
Petersburg  Academy  of  Sciences.  The  Lodyguine 
burner  consisted  of  a  single  rod  of  carbon  diminishing 
in  section  at  the  incandescent  part ;  and  two  or  more  of 
these  rods  were  placed  in  a  globe  provided  with  an  ex- 
terior rheotome,  in  order  that  the  current  might  be 


*  The  Starr- King  system  of  lighting  included  a  generator  of  electri- 
city some  of  the  devices  of  which  are  variously  used  at  the  present  day. 
The  following  summary  of  the  leading  points  of  Starr's  English  patent, 
taken  out  by  King  in  1846  (No.  11,188),  and  entitled  "Improvements  in 
the  Production  of  Magneto-Electricity,"  is  of  interest  : 

1.  The  principle  of  the  machine  consists  in  revolving  between  the  poles 
of  permanent   magnets,    arranged   radially,  a  disk  having  near  its    edge 
bobbins  with  their  axes  parallel  to  the  axis  of  rotation. 

2.  Winds  around  the  iron  cores  a  continuous  flat  strip  of  copper,  in- 
serting cotton  between  each  layer  to  insulate. 

3.  Collects  the  current  from  the  separate  bobbins  with  separate  springs, 
to  allow  of  subdivision,  if  necessary. 

4.  To  prevent   neutralizing   currents   being  induced   in   the   brass   or 
other   metallic    plate   which  forms   the  wheel   carrying   the  armatures,  a 
saw-cut  is  made  from  the  edge  to  the  hole  in  which  the  armature  is  in- 
serted. 

5.  Attaches  a  soft-iron  bar  to  the  inducing  magnets,  so  that  they  may 
each  act  a  second  time  on  any  armature  during  each  revolution. 

f  Meanwhile  both  Shepard  in  1850,  English  patent  No.  13,302,  and 
Roberts  in  1852,  English  patent  No.  14,198,  invented  and  experimented 
with  incandescent  carbon  lamps. 


INCANDESCENT  LAMPS. 


59 


passed  through  a  fresh  carbon  when  one  should  have 
been  destroyed.  Unaccountably,  Lodyguine  has  been 
severely  criticised  by  many  writers,  who  have  pro- 
nounced his  apparatus  the  least  practical  and  the  least 


faora 

Fig.  36.  The 
Starr-King  Burn- 
er, 1845. 


Fig.  37.  The  Konn  Lamp. 


studied  of  all ;  whereas  it  was  the  most  practical  and 
the  most  studied  of  all  that  had  preceded  it,  for  Lody- 
guine recognized  the  value  of  a  perfect  connection  with 
the  incandescent  portion,  such  as  results  from  enlarge- 
ment of  the  carbon  at  the  points  of  contact  with  the 


60  ELECTRIC  LIGHTING  BY  INCANDESCENCE. 

conductors  leading  to  it,  and  he  provided  for  the  inev- 
itable destruction  of  the  rod  by  arranging  another  to 
take  its  place. 

After  Lodyguine  came  Konn  and  Kosloff,  whose  in- 
ventions do  not  diifer  essentially,  although  the  Konn 
lamp  of  1875  (Fig,  37)  was  perhaps  the  moie  practicable. 
This  lamp  consists  of  a  base,  A,  in  copper,  on  which  are 
fixed  two  terminals  to  which  the  conductors  are  fas- 
tened ;  two  bars,  C  D,  in  copper ;  and  a  small  valve,  K, 
opening  only  from  within  outwards.  A  globe,  B,  ex- 
panded at  its  upper  part,  is  clamped  to  the  base  by 
means  of  a  collar,  L,  pressing  on  soft  rubber  washers. 
One  of  the  vertical  rods,  D,  is  insulated  from  the  base, 
and  communicates  with  a  terminal,  also  insulated.  The 
other  rod,  C,  is  constructed  in  two  parts :  (1)  of  a  tube 
fixed  directly  upon  the  base  and  in  electrical  connec- 
tion therewith ;  and  (2)  of  a  copper  rod  split  for  a  part 
of  its  length,  whereby  is  obtained  sufficient  elasticity  to 
permit  the  rod  to  slide  freely  and  yet  be  held  in  place  in 
the  tube.  Carbon  pencils,  E,  are  placed  between  two 
small  plates  which  crown  the  rods.  Each  pencil  is  intro- 
duced into  two  small  blocks,  O,  also  of  carbon,  which 
receive  the  copper  rods  F  G  at  their  extremities.  The 
rods  G-  are  equal  in  length,  and  the  rods  F  are  of  une- 
qual length.  A  hammer,  I,  is  hinged  on  the  bar  C,  and 
makes  connection  only  with  a  single  pencil  of  carbon  at 
once. 

When  the  lamp  is  placed  in  circuit,  a  pencil  of  carbon, 
^  is  traversed  by  the  current ;  and  when  this  pencil 
is  consumed  and  drops  out  of  place,  the  hammer,  I, 
makes  connection  with  another  pencil ;  when  all  the  car- 


INCANDESCENT  LAMPS. 


61 


bons  have  been  consumed  the  hammer  rests  upon  the 
copper  rod  H,  and  the  circuit  is  not  interrupted.  Ac- 
cording to  M.  Fontaine,  the  maximum  light  obtainable 
from  a  Konn  burner  is  equal  to  about  175  candles.  The 


ft1QTO~t.N  G-tiUim* 

Fig.  38!  The  Bouliguine  Lamp. 


Fig.  39.  Fontaine's  Lamp. 


carbon  is  protected  by  partially  exhausting  the  air  and 
depending  upon  the  carbon  monoxide,  subsequently 
formed,  to  preserve  it  from  further  change — an  error  in 
calculation  which  it  is  difficult  to  understand,  and  the 
fallacy  of  which  is  proved  by  the  results.  The  average 
duration  of  the  first  pencil  is  about  twenty  minutes. 


62  ELECTRIC  LIGHTING  BY  INCANDESCENCE. 

The  succeeding  pencils  have  each  an  average  life  of  two 
hours. 

Next  in  practical  order  comes  the  Bouliguine  lamp 
(Fig.  38),  in  which  a  long  pencil  of  carbon  is  fed  upwards, 
as  in  the  Werderamnn  lamp,  through  an  elastic  contact, 
in  this  case  controlled  electro-magnetically.  The  sealing 


Fig.  40.  Farmer's  Lamp,  1879. 

of  the  globe  is  effected,  as  in  the  Konn  lamp,  by  the 
lateral  pressure  of  soft  rubber  washers.* 

The  last  of  these  old  lamps  of  which  there  is  record 
is  the  invention  of  M.  Fontaine  (Fig.  39),  in  which  the 
carbon  pencils,  A  A,  are  held  in  rigid  contacts.  No 

*  Carbon-holders,  made  in  the  form  of  long  tubes  and  filled  with  long 
carbons,  were  first  employed  by  Staite  (English  patent  No.  12,212  of  1848), 
who,  with  his  associate,  Edwards,  was  much  in  advance  of  the  day  in 
which  he  worked. 


INCANDESCENT  LAMPS.  63 

allowance  is  made  for  expansion  or  contraction  of  the 
conductors.  In  this  lamp,  as  in  Lodyguine's,  a  fresh 
pencil  is  brought  into  circuit  by  an  exterior  rheotome 
when  one  has  been  consumed. 

Among  all  these  lamps  that  of  Konn  maintains  its  su- 
premacy ;  and  it  must  be  confessed  that,  considering  the 
time  and  means  devoted  to  the  solution  of  this  problem 
in  European  countries,  the  product  is  insignificant. 

The  lamp  illustrated  in  Fig.  40,  which  was  patented 
by  Farmer,  March  25,  1879,  has  not  progressed  beyond 
the  stage  of  laboratory  experiment.  It  is  perhaps  less 
practical  than  the  lamps  of  Konn  and  others,  in  these 
respects :  that  the  incandescent  rod  or  pencil  is  held 
between  large  blocks  of  carbon  in  such  a  manner  as  to 
greatly  obscure  the  light ;  and  that  the  sealing  is  ef- 
fected by  means  of  a  rubber  stopper  through  which  pas& 
the  conducting  supports,  which,  being  good  conductors 
of  heat,  must  inevitably  cause  the  lamp  to  unseal. 


CHAPTER  Y. 

CARBONS  FOK  INCANDESCENT  LIGHTING. 

"BEFORE  entering  upon  a  further  survey  of  the  field  of 
incandescent  lighting,  it  is  well  that  we  should 
pause  to  consider  the  primal  element  of  all  incande- 
scent lamps — the  luminous  carbon  conductor.  Its  re- 
quirements are  simply  expressed.  In  cross-section 
it  must  be  uniform  and  in  homogeneity  perfect.  The 
denser  and  harder  the  carbon  the  more  lasting  it  proves 
to  be  ;  and  density,  hardness,  and  homogeneity  in  the 
carbon  are  therefore  the  elements,  or  a  part  of  them,  of 
success.  Before  the  time  of  Foucault,  who  substituted 
gas-retort  carbon  for  wood  charcoal,  the  voltaic  arc  was 
little  more  than  a  laboratory  toy  ;  and  thus  with  incan- 
descent lighting,  so  long  as  the  luminous  conductor  ia 
confined  to  the  product  of  the  gas-retort  its  uses  must 
be  confined  to  the  laboratory. 

One  of  the  earliest  methods  of  preparing  artificial  car- 
bons, and  that  in  most  general  use  at  the  present  day, 
consists  in  reducing  coke  to  a  fine  powder  and  thorough- 
ly incorporating  it  with  molasses  or  other  glutinous  hy- 
drocarbon substance.  The  resultant  mixture  is  pressed 
into  moulds  and  baked,  and  afterwards  placed  in  a  con- 
centrated solution  of  the  same  hydrocarbon,  and,  when 
thoroughly  saturated,  again  baked ;  and  so  on  until  it 

64 


CARBONS  FOR  INCANDESCENT  LIGHTING.  65 

acquires  the  requisite  solidity  and  smoothness.  Such 
carbons  are  imperfect,  since  they  contain  many  im- 
purities. 

By  the  Jacquelin  process  carbon  is  produced  which, 
in  purity,  density,  hardness,  and  homogeneity,  is  all  that 
could  be  desired.  M.  Jacquelin,  with  pure  hydrocar- 
bons, closely  imitates  the  processes  of  the  gas-retort,  de- 
composition of  the  compound  gases  being  accomplished 
in  a  highly-heated  porcelain  tube,  upon  the  interior  sur- 
face of  which  the  carbon  is  deposited.  The  objection 
to  this  process  consists  in  the  difficulty  of  reducing  the 
mass  thus  formed  to  the  shape  of  rods  or  pencils,  as  the 
carbon  obtained  is  so  hard  that  it  can  be  cut  only  with, 
the  greatest  difficulty.* 

The  best  artificial  carbons  for  incandescent  lighting 
that  we  have  obtained  are  made  by  the  Carre  process, 
and  supplied  by  M.  Breguet  in  mechanically  perfect 
round  pencils  of  from  eight  to  twenty  inches  in  length,, 
and  almost  any  desired  diameter  in  millimetres  ;  but  in 
these  carbons  there  is  room  for  extensive  improvement 
which,  no  doubt,  M.  Carre  will  turn  to  advantage.  Ac- 
cording to  Fontaine,  the  process  of  manufacture  is  as 
follows :  A  composition,  consisting  of  very  finely  pow- 
dered coke,  calcined  lamp-black,  and  a  syrup  formed  of 
twelve  parts  of  gum  and  thirty  of  cane-sugar,  is  tho- 
roughly ground  and  intermixed,  and  sufficient  water  is 
added  to  give  the  required  consistency.  Thus  prepared 

*. Within  a  few  days  we  have  experimented  with  a  smooth  disk  of  cellu- 
loid, revolving  at  a  high  rate  of  speed,  and  we  find  that  by  means  of  it  the 
hardest  retort-carbon  is  as  easily  and  smoothly  cut  as  so  much  hard  rubber.. 
This  would  seem  to  promise  a  similar  result  with  Jacquelin  carbons. 


66  ELECTRIC  LIGHTING  BY  INCANDESCENCE. 

the  paste  is  compressed  and  passed  through  a  die-plate, 
whereby  the  pencil  is  formed.  Subsequently  the  pencil 
is  subjected  to  a  high  temperature  in  a  crucible,  and  by 
various  operations  and  repetitions  of  the  heating  the 
requisite  density  and  hardness  are  obtained.  The  ar- 
rangement of  the  pencil  for  baking,  after  forming,  while 
yet  in  a  pliable  condition  and  without  permitting  it  to 
twist  or  bend,  is  one  not  fully  understood ;  and  all  at- 
tempts in  this  country  towards  duplicating  the  manu- 
facture have  signally  failed.  Pencils  of  one  thirty-sec- 
ond of  an  inch  in  diameter  and  nine  inches  in  length, 
made  expressly  for  us,  are  as  absolutely  straight  and  re- 
gular as  a  wire  under  tension. 

The  drawn  or  moulded  pencils  are  primarily  placed  in 
a  horizontal  position  on  a  bed  of  coke-dust  in  crucibles, 
each  layer  being  separated  from  its  neighbor  by  an 
intervening  sheet  of  paper.  Secondly,  a  layer  of  coke- 
dust  is  spread  over  the  carbons;  and,  lastly,  the  whole  is 
covered  by  silicious  sand.  Having  been  kept  at  a  cher- 
Ty-red  heat  for  four  or  five  hours,  the  carbons  are  re- 
moved to  a  vessel  of  boiling-hot,  concentrated  caramel 
or  sugar-cane,  and  there  left  for  two  or  three  hours,  the 
syrup  being  alternately  cooled  and  heated  several  times, 
in  order  that  it  may  completely  permeate  the  pores  of 
the  carbons.  Subsequently  the  syrup  is  drawn  off,  and 
any  sugar  adhering  to  the  surface  of  the  carbons  is  re- 
moved by  immersion  in  boiling  water.  Finally,  after 
drying  in  an  oven,  whose  temperature  attains  to  80°  C. 
only  in  the  course  of  twelve  to  fifteen  hours,  the  baking 
operation  is  repeated.  Upon  the  number  of  repetitions 
of  this  process,  to  a  certain  extent,  depends  the  value  of 


CARBONS  FOR  INCANDESCENT  LIGHTING.  (57 

the  carbons,  which,  specially  manufactured,  are  marvels 
of  purity,  tenacity,  density,  and  homogeneity.* 


*  The  following  synopsis  of  old  English  patents  relating  to  electric-light 
carbons,  taken  from  Col.  Bolton's  report,  will  doubtless  prove  of  interest: 
1846.   GREENER  AND  STAITE,  11,076.    "Certain  Improvements  in  Ignition, 
and  Illumination." 

Uses  lamp-black,  charcoal,  or  coke,  already  purified  from  sulphur 
and  metallic  mixtures  by  the  application  of  electricity  in  accord- 
ance with  the  process  patented  by  Jabez  Church  in  1845 ;  digests  in 
nitro  muriatic  acid ;  washes  several  times  in  water  or  in  some  weak 
alkaline  solution,  or  carburetted  alkaline  solution,  finally  with  dis- 
tilled water;  then  dries  and  presses  with-hydraulic  screw,  or  fly-press, 
into  cylinders,  and  when  necessary  exposes  to  intense  heat  in  a  fur- 
nace for  twenty- four  hours. 

1846.  STAITE,  11,449.    Takes  equal  quantities  of  coal  of  a  medium  quality 
(neither  too  rich  nor  too  poor)  and  of  that  purified  description  of 
coke  known  as  "  Church's  Patent  Coke";  powders  and  compresses  in 
close  sheet-iron  moulds  until  solid,  then  plunges  into  concentrated 
solution  of  sugar,  and  when  sufficiently  dry  subjects  it  for  several 
hours  in  a  close  vessel  containing  charcoal  at  an  intense  white  heat. 

1847.  STAITE,  11,783.     In  addition  to  pressing,  also  heat,  and  when  hot 
plunge  into  sugar  melted  by  heat  without  the  aid  of  any  liquid. 
Then  cool  and  place  in  a  closed  vessel  containing  pieces  of  charcoal 
heated  to  a  white  heat,  and  keep  there  for  many  hours,  or  even  two  or 
three  days;  or  the  whole  mass  may  be  a  second  time  immersed  in 
melted  sugar  and  the  process  repeated. 

He  says,  also,  that  electrodes  made  of  gas-retort  carbon  frequently 
contain  iron,  which  makes  them  split  and  not  give  out  so  much  light. 
They  may  be  much  improved  by  heating  to  a  white  heat  in  a  closed 
vessel  for  some  days.  , 

1848.  STAITE,  12,212.     Prefers  to  use,  1st,  plumbago  powder  having  iron, 
etc.,  extracted  by  washing  and  warming  in  acids;  2d,  lamp-black; 
3d,  charcoal  powder;  4th,  powder  of  carbonaceous  concrete  which  is 
deposited  in  gas-retorts;  or,  5th,  sifted  grains  of  this  material.     Mix 
any  one  of  these  with  brown  sugar,  melt  and  boil  (without  water) 
until  stiff,  press  when  hot  in  iron  moulds  lined  inside  with  paper, 
chalk,  or  plaster-of-Paris  to  prevent  adherence  and  to  allow  for  es- 
cape of  the  gas,  the  moulds  having  holes  for  the  same  purpose.     Heat 
slowly  until  a  red  heat  is  obtained,  at  which  temperature  keep  them 
for  some  time,  then  take  out  and  put  in  upright  crucibles  with  lute; 
gently  raise  to  a  white  heat,  at  which  temperature  keep  them  for 
sonie  time,  and  then  allow  them  to  cool. 


£8  ELECTRIC  LIGHTING  BY  INCANDESCENCE. 

The  lack  of   a  better  carbon  than  retort  carbon  di- 

1848.    LE  Mor/r,  12  219.     "  Constructing  Electric  or  Galvanic  Piles  for  ob- 
taining Electric  Light." 

Take  one  part  of  coal,  coke,  or  charcoal,  three  parts  of  carbon  ob- 
tained from  gas  retorts,  ground  fine,  and  one  of  tar;  mould  and  press, 
dry  in  the  shade,  heat  gradually  in  a  nearly  closed  retort  until  brought 
to  a  red  heat,  at  which  temperature  keep  the  retort  for  thirty-six 
hours,  when  cool  slowly. 

Makes  the  carbon  disks  used  by  him  in  his  electric  lamp  from  gas- 
retort  carbon,  cut  into  the  right  shape,  and  purified  by  solution  in  a 
mixture  of  nitric  and  muriatic  acids  for  twelve  hours,  afterwards  in 
fluoric  acid  for  twelve  hours. 

1852.   ROBERTS,  14,198.    "  Improvements  in  the  production  of  Electric  Cur- 
rents in  obtaining  Light,"  etc. 

Mixes  five  per  cent,  of  lime  with  materials  of  electrodes,  to  in- 
crease the  brilliancy  of  the  light. 

1852.  JACKSON,   14,330.     "Improvements  in  producing  Artificial  Light," 
etc. 

Hollows  out  top  of  lower  carbon  and  introduces  mercury  or  plati- 
num into  the  recess. 

1853.  BINKS,  119.      "  Improvements  in  producing  Electric  Light."    Pro- 
visional protection  only. 

Subjects  lignite  to  destructive  distillation  in  closed  vessels. 

Covers  metal  with  tar,  pitch,  bitumen,  asphalt,  and  rosin,  or  mix- 
tures of  finely-pulverized  charcoal  or  lamp-black,  with  some  adhesive 
material,  which  on  being  dried  or  strongly  heated  leaves  a  residue  of 
solid  or  compact  carbon, 

Or  drills  holes  in  carbon  and  inserts  metal  rods,  or  attaches  a  ve- 
neering of  charcoal  to  metal. 
1853.   STAITE,  634.    Boils  carbon  in  oil  or  other  fatty  substance,  and-  bakes. 

1857.  HARRISON,  588.     "  Improvements  in  obtaining  Light  by  Electricity." 

Pieces  of  metal  or  other  material  are  placed  in  gas-retorts,  or  in 
tubes  connected  therewith,  for  the  purpose  of  receiving  a  deposit  of 
gas  carbon.  Or  a  combination  of  metal  powder  and  plumbsigo,  or 
other  form  of  carbon,  may  be  formed  into  electrodes  by  compression. 
Proposes  to  insert  other  substances  in  the  powder  in  order  to  color 
the  light. 

1858.  HUNT,  282.     "Improvements  in  Means  for  Producing  the  Electric 
Light." 

The  residuum  from  the  distillation, of  tar  or  pitch  is  reduced  to  an 
impalpable  powder,  and  mixed  with  tar  or  other  hydrocarbon ;  the 
electrodes  are  then  moulded,  heated  red  hot,  immersed  in  tar  and 
again  heated,  and  so  on  until  the  required  density  is  obtained. 


CARBOXS  FOR  INCANDESCENT  LIGHTING.  69 

rected  our  attention  to  new.  processes  of  manufacture, 
resulting  in  the  granting  of  Letters- Patent  to  Sawyer  & 
Man  in  January,  1879,  for  a  process  belieyed  to  be  new  in 
physics.  In  many  experiments  previously  ma(le,  incan- 
descent lamps  had  been  charged  with  an  atmosphere  of 
illuminating  gas,  naphtha,  and  other  hydrocarbon  vapors, 
both  at  atmospheric,  pressure  and  under .  partial  exhaus- 
tion, with  a  view  to  arresting  consumption  of  the  carbon 
pencil.  .  It  was  found  that  the  globe  soon  blackened,  and 
this  to  an  extent  commensurate  with  the  amount  of  the 
•confined  gas  or  vapor,  while  the  carbon  pencil  became  of 
a  bright  gray  color,  but  otherwise  suffered  no  change.  It 
thus  appeared  that  the  deposit  which  blackened  the 
globe  could  not  have  proceeded  from  the  pencil ;  and  in- 
vestigation showed  that  the  hydrocarbon  atmosphere 
liad  been  decomposed,  the  hydrogen  set  free,  and  the  car- 
Ibon  deposited;  and  inferentially  it  appeared  that  the 
gray  color  of  the  pencil  was  due  to  the  mechanical  com- 
bination with  it  of  a  portion  of  the  dissociated  carbon. 

By  easy  advances  the  conclusions  were  reached  that 
if  there  was  any  deposit  upon  the  pencil  from  any  given 
volume  of  gas,  there  would  be  a  greater  deposit  from  a 
greater  volume  of  gas ;  and  that  the  greater  the  heat 
developed  in  the  pencil,  and  the  slower  the  deposition, 
the  more  dense  and  perfect  would  be  the  carbon.  These 
conclusions  were  subsequently  verified.  It  was  found 
that  In  a  stream  of  hydrocarbon  gas  or  vapor  an  im- 
perfect pencil  of  carbon  was  rendered  perfect,  the  ori- 
ginal points  of  imperfection,  being  of  proportionate- 
ly high  resistance  and  heating  proportionately  to  a 
higher  degree  than  the  perfect  portions,  receiving  a  de- 


70  ELECTRIC  LIGHTING  BY  INCANDESCENCE. 

posit  which  compensated  for  such  imperfection.  Thus 
pencils  of  carbon  of  any  desired  diameter  up  to  one- 
eighth  of  an  inch,  and  of  a  density  and  homogeneity  be- 
fore unthought-of,  and  capable  of  taking  a  polish  like  jet, 
were  formed  of  and  upon  a  mere  filamentary  conductor. 
The  original  filament  appeared  to  be  unchanged,  the  de- 
posit carbon  being  in  the  form  of  a  cylinder  surrounding 
it  and  possible  to  be  broken  off  from  it. 

It  was  found  also  that  the  pencil  could  be  as  veritably 
welded  or  joined  to  the  connecting  carbon  blocks  as 
two  pieces  of  metal  are  welded  or  joined  together,  and 
the  Sawyer- Man  carbon  horseshoe,  which  was  perfected 
and  exhibited  in  the  winter  of  1878-9,  was  treated  by 
this  process,  the  ends  of  the  horseshoe  being  welded  to 
the  supporting  blocks  in  order  to  secure  perfect  elec- 
trical contact. 

From  obtaining  a  cylindrical  deposit  of  carbon  upon  a 
filament  of  ordinary  carbon,  the  manufacture  of  pencils 
entirely  of  deposit  carbon  was  attempted.  The  cylinder 
was  sawed  through  lengthwise  by  means  of  a  rapidly- 
revolving,  smooth,  thin  disk  of  steel,  and  the  original 
filament  removed.  The  two  portions,  semicylindrical 
in  shape,  remaining,  were  then  subjected  to  treatment. 
The  most  perfect  of  all  these  carbons  were  prepared  by 
taking  sticks  of  fine  willow  charcoal,  and  first  saturating 
the  same  with  syrup  and  subjecting  to  heat  as  in  the 
Carre  process,  in  order  to  increase  their  conductivity. 
The  sticks  were  then  divided  into  pieces  one-half  an  inch 
in  length  and  three  sixty-fourths  of  an  inch  in  diam- 
eter, and  placed  between  carbon-holders,  for  treatment. 
Heated  to  extreme  incandescence  and  surrounded  by  an 


CARBONS  FOR  INCANDESCENT  LIGHTING. 


71 


atmosphere  of  hydrocarbon,  the  deposit  described  imme- 
diately formed.  The  pencil, 
with  shining,  rounded  ends, 
was  then  filed  on  one  side  until 
the  original  willow  was  ex- 
posed, but  leaving  the  ends  of 
the  pencil  untouched.  The  wil- 
low being  next  removed,  a  pen- 
cil of  boat  shape  and  remark- 
able durability  was  obtained. 
The  Sawyer-Man  lamps,  as  ex- 
hibited in  New  York,  were  all 
furnished  with  carbons  of  this 
character,  and  to  the  perfection 
of  these  boat- shaped,  electri- 
cally-formed carbons  was  due 
their  comparative  success.  To 
the  necessity  of  frequent  re- 
newal, and  the  time  and  skill 
required  to  produce  the  car- 
bons, was  due  the  commercial 
failure  of  these  lamps. 

In  preparing  long  pencils  of 
carbon,  allowance  must  be  made 
for  the  expansion  of  the  origi- 
nal filament.  The  Sawyer  de- 
positing apparatus  (Fig.  41), 

which  holds  the  filament,  is  en- 
Fig.  41.  Carbon-Treating  Apparatus. 

tirely  immersed  in  a  hydrocar- 
bon bath.  The  decomposing  current,  entering  by  way  of 
the  metallic  uprights  fixed  to  a  soapstone  base,  passes 


72  ELECTRIC  LIGHTING  BY  INCANDESCENCE. 

through  the  filament  by  way  of  its  carbon-clamps.  The 
upper  clamp,  balanced  on  a  knife-edge,  is  removable.  In 
this,  when  removed,  one  end  of  the  filament-' is  secured 
and  the  clamp  ds  then  put  in  position.  Next  the  lower 
end  of  the  filament  is '  swung  between  the  jaws  of  the 
lower  fixed  clamp,'  and,  this  having  been  tightened,  the 
cam-lever  above  is  thrown  up.  and  the  filament  thus 
placed  under  tension.  When  the  current  is  applied 
there  ensues  violent  ebullition  of  the  liquid  composing 
the  bath,  due  to  the  rapid  disengagement  of  hydrogen  ; 
dense  volumes  of  smoke  arise,  and  in  from  fifteen  to 
thirty  seconds  the  filament  is  covered  with  a  shell  of  de- 
posit carbon  from  one  sixty -fourth  to  one  thirty-second 
of  an  inch  in  thickness.  Olive-oil  is  the  best  hydrocar- 
bon for  this  treatment.  Next  in  order  of  efficiency, 
among  common  hydrocarbons,  are  the  following  : 

Refined  sperm  oil ; 

Absolute  alcohol ; 

Naphtha  and  gasoline  ; 

Turpentine. 

In  using  the  last-named  hydrocarbons,  great  care 
must  be  taken  not  to  overheat  the  bath,  and  to  see  that 
the  filament  is  wholly  immersed  before  applying  the 
current,  otherwise  there  is  danger  of  fire  and  explosion. 
The  carbonizing  of  live  willow  twigs,  with  a  view  to 
obtaining  a  suitable  bent  carbon,  by  Sawyer  &  Man,  and 
the  carbonizing  of  paper  and  bamboo  by  Edison,  substan- 
tially close  the  account  of  incandescent  carbons.  Re- 
cently, an  attempt  to  better  the  texture  of  the  filament 
has  been  made  by  Mr.  J.  W.  Swan,  of  Newcastle-on- 
Tyne,  who  forms  it  from  cotton  thread,  which  is  sub- 


CARBONS  FOR  INCANDESCENT  LIGHTING.  73 

jected,  previous  to  carbonization,  to  the  action  of  sul- 
phuric acid  in  order  "  to  produce  the  same  kind  of  effect 
of  semi-solution  and  the  welding  together  of  the  cellulose 
fibre  as  is  produced  in  making  vegetable  parchment  from 
bibulous  paper." 

The  behavior  of  carbon  at  different  temperatures  is 
strikingly  similar  to  the  behavior  of  glass  at  proportion- 
ate temperatures,  similar  results  in  the  latter,,  however, 
being  attained  at  much  lower  temperatures  than  in  the 
former.  As  examples  the  following  facts  are  cited: 
In  hardness  and  brittleness,  glass  and  homogeneous 
carbon  at  ordinary  temperatures  are  substantially  alike. 
Glass,  drawn  into  fine  threads,  and  carbon  in  filaments, 
may  be  bent,  and  to  a  certain  extent  twisted,  with- 
out  breaking.  Glass  and  carbon,  heated  and  twisted  or 
bent,  retain  the  changed  form  and  their  normal  strength 
at  the  point  of  twisting  or  bending,  upon  cooling.  Glass 
moderately  heated,  and  carbon  intensely  heated,  if  given 
a  blow,  fly  into  fragments. 

Glass  and  carbon  are  better  conductors  of  electricity 
when  intensely  heated  than  when  at  ordinary  tempe- 
ratures. 

A  ten-inch  pencil  of  carbon,  heated  to  extreme  incan- 
descence, expands,  under  slight  tension,  to  a  length  of 
10J  inches.  Upon  cooling  it  does  not  return  to  its  origi- 
nal dimensions,  but  only  slightly  contracts. 


CHAPTER  VI. 

NEW   FORMS   OF  LAMPS. 

TT  was  in  1875,  after  some  desultory  work,  that  we  first 
took  an  active  interest  in  the  subject  of  incandescent 
lighting.  Subsequent  years  devoted  to  the  perfection 
of  apparatus  in  connection  therewith  have  greatly  aug- 
mented the  stock  of  knowledge  originally  possessed. 
The  theories  upon  which  experimentalists  had  labored, 
and  the  probable  causes  of  their  failures,  were  given  care- 
ful consideration,  and  in  all  matters  of  doubt  the  results 
of  practical  experiment  were  made  the  basis  of  conclu- 
sions. 

It  did  not  at  first  appear  that  when  a  carbon  conductor 
is  excluded  from  contact  with  combining  matter,  it  is 
nevertheless,  in  the  sense  of  changing  form,  destructible  ; 
otherwise  speaking,  the  destructibility  of  all  matter  sub- 
jected to  constant  and  varying  tension  did  not  primarily 
present  itself  with  the  convincing  force  that  is  born  of  ex- 
perience. Many  experimenters  in  incandescent  light- 
ing had  failed  because  they  had  overlooked  the  fact 
that  nothing  is  indestructible,  or  undisintegra  table,  or 
unchangeable.  Additionally,  the  Starr-King  lamp  had 
failed  because  there  was  present  in  the  Toricellian  va- 
cuum the  vapor  of  quicksilver,  due  .to  heat,  with  which 
the  carbon  entered  into  chemical  combination.  Lody- 
guine  obviated  an  imperfect  contact  with  the  carbon 


NEW  FORMS  OF  LAMPS.  75 

conductor  by  making  the  luminous  section  a  reduced 
portion  of  a  large  carbon.  Lodyguine,  Konn,  Kosloff, 
and  Bouliguine,  recognizing  the  destructibility  of  the 
conductor,  sought  compensation  in  self-renewing  de- 
vices ;  but  their  lamps  were  imperfect  in  that  they  did 
not  preserve  the  carbon  from  contact  with  gases  with 
which,  at  high  temperatures,  it  enters  into  chemical 
combination.  All  of  the  old  lamps,  excepting  that  of 
Starr-King,  were  inadequately  sealed.  All  were  some- 
where attended  by  conditions  calculated  to  prevent  the 
realizations  sought. 

To  preserve  incandescent  carbon  from  chemical  change, 
it  must  be  hermetically  sealed  in  vacuo,  or  in  a  globe 
containing  a  pure  and  perfectly  dry  cyanogen,  nitrogen, 
hydrogen,  or  hydrocarbon  atmosphere.  If  there  is  a  trace 
of  oxygen  or  other  gas  or  vapor  present,  or  any  third 
non-gaseous  body  in  condition  to  come  in  contact  with 
the  carbon,  chemical  change  is  the  result.  Nor  can  the 
incandescent  carbon  establish  connection  with  any  metal, 
for  the  reason  that  the  carbide  of  that  metal  is  then  form- 
ed. Its  connections  must  be  with  carbon  of  greater  mass, 
in  order  that  the  temperature  of  the  metal  contacts  may 
be  low  and  the  contacts  perfect ;  and  it  must  itself  be 
pure  and  also  homogeneous,  as  imperfections  in  its  struc- 
ture produce  consequent  points  of  resistance  at  which  the 
current  concentrates  and  where  disintegration  occurs. 
In  the  dioxide  of  carbon  (carbonic  acid  gas),  which  in- 
stantly extinguishes  ordinary  flame,  the  incandescent 
conductor  is  consumed,  not  quite  so  rapidly,  but  just  as 
surely,  as  in  air.  In  the  monoxide  of  carbon  consump- 
tion is  certain,  though  still  less  rapid.  The  explanation 


76  ELECTRIC  LIGHTING  BY  INCANDESCENCE. 

of  this  is  found  in  the  fact  that  a  current  of  the  heated 
atmosphere  is  constantly  flowing  past  the  conductor,  and 
the  heat  of  the  conductor  is  so  great  that  the  carbonic 
oxide  is  decomposed  before  the  two  come  in  contact ; 
and  the  oxygen  thus  set  free,  and  having  a  higher  affi- 
nity for  the  carbon  of  the  conductor  than  for  the  less 
heated  atom  from  which  it  has  been  dissociated,  com- 
bines with  the  former,  while  the  dissociated  carbon  atom 
is  deposited  either  upon  the  interior  works  of  the  lamp 
or  upon  the  inner  surface  of  the  enclosing  globe  ;  or  the 
oxygen  rises  in  a  free  state  (the  carbon  being  deposited 
as  described),  and  upon  subsequently  coming  in  contact 
with  the  incandescent  conductor  thereupon  combines  with 
it  to  form  the  monoxide.  The  monoxide,  not  the  diox- 
ide, is  always  formed  when  there  is  a  limited  amount  of 
oxygen  present.  Thus  it  will  be  clear  that,  however 
slight  may  be  the  trace  of  oxygen  in  the  sealed  globe 
of  an  electric  lamp,  and  however  great  in  mass  the  in- 
candescent carbon  may  be,  it  is  only  a  question  of  time 
when  this  circular  process  of  chemical  dissociation  and 
recombination  will  entirely  destroy  the  conductor  and 
deposit  it  upon  the  interior  works  and  the  globe  of  the 
lamp.  What  occurs  with  oxygen  occurs  with  other  sub- 
stances having  an  affinity  for  carbon  at  high  tempera- 
tures ;  and  to  procure  a  non-combining  atmosphere  suffi- 
ciently free  from  impurities  involves  a  very  delicate 
laboratory  process.  The  employment  of  hydrogen  is  dis- 
advantageous in  these  respects,  that .  it  necessitates  a 
more  powerful  current  to  produce  a  given  light  than 
when  the  conductor  is  in  vacuo  or  surrounded  by  nitro- 
gen, and  that,  should  any  leak. occur,  air  sufficient  to 


NEW  FORMS  OF  LAMPS.  77 

form  a  dangerous  explosive  mixture  soon  finds  access 
to  the  globe.  For  the  latter  reason  an  hydrocarbon  at- 
mosphere is  impracticable,  in  addition  to  the  fact  that 
the  decomposition  of  the  hydrocarbon  so  blackens  the 
globe  as  to  greatly  obscure  the  light.  The  incandescent 
carbon,  therefore,  can  only  be  practically  employed  in 
vacuo,  or  surrounded  by  an  atmosphere  of  pure  nitrogen, 
or  in  a  partial  or  nearly  perfect  vacuum  of  hydrogen, 
nitrogen,  cyanogen,  or  hydrocarbon  gas,  which  last, 
however,  speedily  becomes  a  vacuum  of  hydrogen,  for 
the  reason  that  the  hydrocarbon  is  decomposed  and  the 
hydrogen  set  free  in  the  lamp. 

The  idea  of  protecting  carbon  from  chemical  change 
by  enclosing  it  in  a  vacuum  or  a  carbon-preservative 
atmosphere  is,  as  has  been  shown,  by  no  means  new. 
Atmospheres  of  nitrogen,  hydrogen,  and  the  carbonic 
oxides,  and  their  vacuums,  as  well  as  the  ordinary 
vacuum,  have  been  employed  in  the  laboratory  for  many 
years,  and  are  common  property  of  which  all  experi- 
mentalists may  avail  themselves.* 

Next  to  preserving  the  carbon  from  chemical  change, 
the  greatest  difficulty  is  found  in  hermetically  sealing 
the  globe  of  the  lamp.  The  sealing  of  glass  upon  plati- 
num is  familiarly  shown  in  Geissler  vacuo-tubes ;  and 
while  the  degree  of  skill  required  for  this  method  of 

*  The  following  data,  abstracted  from  the  report,  of  Colonel  Bolton  to  the 

London  Society  of  Telegraph  Engineers,  March  26,  1879,  refer  to  expired 

English  patents  relating  to  incandescent  lighting: 

1841.  DE  MOLEYNS,  9,053.  Uses  a  coil  of  platinum  wire  at  the  base  of 
which  is  a  piece  of  spongy  platinum  and  into  which  falls  a  shower  of 
finely-pulverized  boxwood  charcoal  or  plumbago,  the  whole  being  en- 
closed in  an  exhausted  tube. 

1845.   KINO,  10,919.     Application  of  continuous  metallic  and  carbon  con- 


78  ELECTRIC  LIGHTING  BY  INCANDESCENCE. 

sealing  is  rare,  the  Geissler  method  is  undoubtedly  as 
perfect  as  any  yet  devised. 

In  the  Edison  lamp  (Fig.  42)  the  Geissler  method  of 
sealing  is  employed,  the  two  conductors,  A  A,  leading 
to  the  carbon  loop,  D,  being  sealed  at  B  B  in  the  glass 
of  the  compound  globe,  E.  In  order  to  obtain  a  per- 
fect connection  with  the  carbon  filament  its  ends  are  en- 
larged and  clamped  in  suitable  blocks,  C.  Exhaustion 
of  the  air  by  way  of  the  neck,  F,  to  the  one  millionth 
of  an  atmosphere,  leaving  in  the  lamp  a  portion  of  oxy- 
gen represented  by  ^01^0-0,  follows.  The  filament  ori- 
ginally used  by  Mr.  Edison  was  prepared  by  cutting 
card-board  into  the  desired  shape,  and  carbonizing  the 
same  by  placing  the  loops  thus  formed  in  layers  within 
an  iron  box,  with  intervening  layers  of  tissue-paper, 
closing  the  box  to  exclude  oxygen,  and  raising  the 
whole  to  red  heat  in  a  furnace.  Lack  of  homogeneity 
in  the  structure  of  these  carbons  subsequently  led  Mr. 
Edison  to  the  adoption  of  carbonized  bamboo- wood, 
which  is  worked  down  by  successive  cutting  and  scra- 
ping until  the  entire  length  of  the  loop  between  its  en- 
larged ends,  which  length  varies  from  five  to  seven  inch- 
es, is  reduced  to  a  uniform  cross-section  of  from  one 

ductors,  intensely  heated  by  the  passage  of  a  suitably  regulated  cur- 
rent of  electricity.  Uses  Toricellian  vacuum  when  carbon  is  em- 
ployed. [King  was  Starr's  agent.] 

1848.   STAITE,  12,212.     Uses  an  iridium  or  an  iridio-platinum  wire. 

1850.  SHEPARD,  13,302.  In  a  ground-glass  globe,  exhausted,  a  vertical  rod 
of  carbon  is,  by  means  of  a  weight,  pushed  down  into  a  small  carbon 
cone  constituting  the  terminal. 

1852.  ROBERTS,  14,198.  Complete  apparatus  for  rendering  a  rod  of  graph- 
ite, coke,  or  charcoal  incandescent  in  a  non-combustible  atmosphere. 
Placing  the  carbon  in  a  deoxygenated  atmosphere  (as  hydrogen  or 
nitrogen),  rarefied,  was  patented  by  Staite  in  1846,  No.  11,499. 


NEW  FORMS  OF  LAMPS. 


79 


sixty-fourth  to  one  thirty-second  of  an  inch.  The  deli- 
cacy of  manipulation  of  the 
wood,  in  order  to  make  the 
filament  uniform  in  size 
throughout,  renders  its  cost 
excessive  ;  but  this  difficulty, 
in  a  measure  at  least,  will 
probably  be  overcome.  The 
resistance  of  the  loop  when 
carbonized  is  from  100  to  300 
ohms,  and  the  amount  of 
light  obtainable,  with  safety 
to  the  conductor,  varies  from 
two  to  ten  candles.  Fig.  43 
is  an  illustration  of  an  Edi- 
son bamboo  filament,  full 
size,  before  bending  and  car- 
bonization. 

In  carrying  out  the  Edison 
method  of  manufacture  a 
glass  bulb  (Fig.  44),  of  the 
size  desired  for  the  enclosing 
globe  of  the  lamp,  is  formed, 
with  a  supporting  neck,  ex- 
tending in  one  direction,  of  a 
diameter  sufficient  to  permit 
the  passage  of  the  illuminat- 
ing conductor  through  it. 
Preferably  a  piece  of  tubing, 
of  the  size  of  the  neck,  has 
Upon  a  point  on  the  bulb  op- 


Fig.  42.  The  Edison  Lamp. 


the  bulb  blown  in  it. 


80 


ELECTRIC  LIGHTING  BY  INCANDESCENCE. 


s 


posite  the  centre  of  the  neck  is  formed  a  long 
tube  for  attachment  of  the  bulb  to  the  air- ex- 
hausting apparatus.  Upon  the  end  of  a  smaller 
piece  of  tubing  a  small  bulb  is  formed,  and  the 
body  of  the  tube,  a  little  below  the  bulb,  is  en- 
larged for  a  small  space  to  about  the  size  of  the 
supporting  neck  of  the  first  bulb.  This  portion 
constitutes  the  loop-supporting  part,  platinum 
wires,  terminating  in  clamps  for  holding  the 
loop,  being  passed  through  it  and  hermetically 
sealed  therein.  After  the  filament  is  in  place,  as 


Fig.  44.  Edison  Outer  Globe. 


Fig.  45.  Inner 
Globe  and  Works, 


NEW  FORMS  OF  LAMPS. 


81 


shown  in  Fig.  45,  the  small  tube  is  passed  up  into  the 
bulb  of  the  large  tube  until  its  further  passage  is  stopped 


Fig.  46.  Globes  joined  together. 


Fig.  47.  Lamp  Sealed. 


by  the  neck  of  the  latter,  when  the  two  are  sealed  to- 
gether by  fusion,  and  appear  as  shown  in  Fig.  46. 
The  mechanical  construction  of  the  lamp  being 


$2  ELECTRIC  LIGHTING  BY  INCANDESCENCE. 

complete,  it  is  attached  to  the  vacuum-pump  by  the  neck 
before-mentioned,  and  when  a  proper  degree  of  exhaus- 
tion has  been  attained,  the  end  of  the  tube  is  softened 
and  sealed  by  heat,  after  which  the  lamp  is  removed  from 
the  pump.  Finally,  the  tube  is  softened  and  sealed  near 
its  point  of  juncture  with  the  globe,  when  the  portion 
remaining  above  is  broken  off  and  the  neck  again  soft- 
ened and  sealed  immediately  above  the  sealing  before 
made  at  the  point  of  juncture.  Fig.  47  shows  the  com- 
pleted lamp. 

The  Maxim  lamp  (Fig.  48),  recently  exhibited  in  New 
York,  differs  from  Mr.  Edison's  in  no  essential  particu- 
lar. The  Geissler  method  of  sealing  is  employed,  and 
the  carbon  filament,  manufactured  from  card-board,  is 
made  in  the  form  of  a  double  loop,  closely  resembling 
the  letter  M.  Thus  prepared,  the  light  obtainable  is 
substantially  the  same  as  that  from  the  Edison  lamp. 
When  the  filament  is  treated  by  immersion  in  hydrocar- 
bon by  the  process  of  depositing  already  described,  its 
section  is  enlarged  and  improved,  and  the  light  then  ob- 
tainable is  from  10  to  30  candles. 

Before  sealing  his  lamp,  Mr.  Maxim  fills  the  globe  with 
the  vapor  of  gasoline,  to  the  exclusion  of  all  air,  and 
finally  exhausts  by  means  of  the  vacuum-pump.* 

Run  at  a  power  of  eight  candles,  in  a  nearly  perfect 

*  An  erroneous  impression,  in  regard  to  the  Maxim  lamp,  due  to  the 
employment  of  gasoline  in  the  process  of  exhaustion,  is  that  it  is  a  self-re- 
newing device — i.e.,  that  whenever  consumption  or  disintegration  occurs, 
the  filament  is  repaired  by  an  ever  present  supply  of  hydrocarbon.  The 
reverse  is  the  case.  When  ready  for  use  the  globe  contains  a  trace  of  gaso- 
line vapor,  and  this  is  almost  immediately  decomposed,  setting  the  hydro- 
gen free,  and  leaving  present  a  trace  of  hydrogen  merely. 


NEW  FORMS  OF  LAMPS. 


83 


vacuum,  the  life-time  of  filamentary  carbons  is  from  ten 
to  one  hundred  hours. 


Fig.  48.  The  Maxim  Lamp. 


^M0  0h^ 

Fig.  49.  The  Sawyer-Man  Lamp. 


The  Sawyer-Man  system  of  lighting  was  exhibited  in 
New  York  in  1878.     Fig.  49  is  an  illustration  of  the  first 


84  ..ELECTRIC  LIGHTING  BY  INCANDESCENCE. 

device  of  these  experimentalists  to  which  publicity  was 
given. 

In  this  lamp  the  enclosing  globe  was  provided  with  a 
flange  constituting  an  integral  part  of  the  globe,  and  a 
disk  of  glass  perforated  with  two  small  holes  was  accu- 
rately ground  to  fit  the  same.  The  ground  surfaces  were 
coated  with  fir  balsam,  and  the  globe  and  stopper 
strongly  clamped  together  by  means  of  bolts  passing 
through  an  elastic  flange  below  the  stopper,  and  a  metal- 
lic flange  bearing  upon  the  glass  flange.  Through  the 
holes  in  the  stopper  passed  the  diminished  ends  of  two 
stop-cocks,  whose  joints  were  made  perfect  by  drawing 
their  shoulders  powerfully  down  upon  paper  washers 
first  thoroughly  impregnated  with  balsam.  Subsequent- 
ly, melted  sealing-wax  was  poured  around  the  whole  of 
the  base.  By  this  means  very  perfect  joints  were  se- 
cured, and  to  retain  them  so  it  was  only  necessary  to  pre- 
vent undue  heating  of  the  parts.  Therefore,  the  con- 
ductors leading  from  the  outside  stop-cock  connections 
to  the  illuminating  part  of  the  lamp  were  given  consider- 
able length  and  large  radiating  surface.  An  insulating 
diaphragm  supported  the  upper  works. 

The  incandescent  carbon  pencil,  one-half  inch  in 
length,  and  varying  in  different  lamps  from  one  thirty - 
second  to  one-twelfth  of  an  inch  in  diameter,  was  held  in 
small  carbon  blocks  let  into  larger  blocks,  one  of  which 
was  fixed  in  the  lower  standard,  and  the  other  in  a  con- 
necting arm,  which,  in  order  to  allow  for  expansion  and 
contraction  of  the  pencil  without  friction,  was  supported 
upon  a  knife-edge  bearing.  This  connecting-arm  was 
held  in  place  by  a  coiled  spring.  The  spiral  conductors 


NEW  FORMS  OF  LAMPS. 


85 


consisted  of  tubes,  one  of  which 
was  provided  with  openings 
along  its  length,  and  each  con- 
necting with  a  stop-cock.  A 
lump  of  metallic  sodium  or  po- 
tassium as  an  absorbent  of  oxy- 
gen; and  its  oxide,  when  formed, 
as  an  absorbent  of  carbonic  acid 
gas,  was  placed  in  the  lamp. 
To  charge  the  lamp,  a  stream  of 
nitrogen  was  caused  to  flow 
through  one  of  the  tubes  to  the 
upper  part  of  the  globe,  escap- 
ing by  way  of  the  openings  in 
the  other  tube.  Carbons  of  a 


Fig.  50.  Lamp  with  fluted  Conductors. 


Fig.  51.  Perfected  Lamp. 


86  ELECTRIC  LIGHTING  BY  INCANDESCENCE. 

density  before  unattained  were  employed  in  this  lamp  ; 
and  although,  through  imperfect  contacts  and  a  faulty 
atmosphere,  many  of  the  lamps  failed  to  last  more  than 
a  few  hours,  some  of  them  were  used  daily  for  several 
weeks  without  exhibiting  marked  change.  In  the  con- 
struction of  the  lamp,  it  was  found  essential  to  round  the 
ends  of  the  carbon  pencil,  and  to  make  a  tapering  cavity 
in  the  small  connecting-blocks,  which  were  firmly  set  in 
the  larger  blocks.  The  final  sealing  of  the  lamp  was 
effected  by  soldering  the  stop-cocks.  Fig.  50  represents- 
the  lamp  in  another  form,  with  radiators  of  copper  rib- 
bon to  prevent  conduction  of  heat  to  the  base ;  and  in 
Fig.  51  is  shown  the  perfected  lamp,  with  small  spiral 
conductors,  in  which  the  soap-stone  was  replaced  by  a 
metallic  diaphragm. 

The  Sawyer-Man  experiments  were  of  an  extensive 
and  diversified  character,  and  among  the  earliest  at- 
tempts to  obtain  a  practicable  lamp  was  the  including 
of  an  arch  or  loop  of  carbon  in  the  circuit  of  the  radi- 
ators (Fig.  52). 

This  carbon  loop  was  originally  employed  in  March, 
1878,  a  rod  of  retort-carbon  being  turned  true  in  a  lathe 
and  bored  out  to  form  a  tube ;  from  this,  thin  flanges 
were  cut,  and  after  being  clamped  between  carbon  wash- 
ers, the  upper  half  was  left  standing  and  the  lower  part 
broken  out.  It  was  not  until  the  following  winter  that 
the  carbonizing  of  different  substances  in  the  form  of  a 
loop,  and  especially  twigs  of  fine  willow,  was  attempted, 
with  varying  results.  A  year  later  Mr.  Edison  greatly 
improved  the  manufacture  of  these  loops  by  processes 
much  better  calculated  to  attain  the  end  desired  than 


NEW  FORMS  OF  LAMPS. 


87 


those  employed  by  Sawyer  &  Man,  whose  success  in  this 
direction  was  limited. 


Pig.  52.  The  Horseshoe  Lamp. 


Fig.  53.  Self -renewing  Lamp. 


The  fact  appearing  that  it  is  only  a  question  of  a  brief 
period  of  time  when  a  carbon  loop  or  pencil  subjected 


88  ELECTRIC  LIGHTING  BY  INCANDESCENCE. 

to  the  action  of  powerful  currents  will  suifer  disintegra- 
tion, it  is  clear  that  some  means  of  renewing  the  incan- 
descent conductor  of  any  lamp  must  be  provided ;  and 
this  renewal  must  be  accomplished  without  destroying 
the  lamp.  To  replace  a  Sawyer-Man  carbon  required  a 
workman' s  time  from  two  to  three  hours,  and  the  re- 
charging of  the  lamp  with  absolutely  pure  nitrogen  cost 
about  seventy  cents,  without  taking  into  consideration 
the  cost  of  the  carbon.  It  was  therefore  an  impractica- 
ble lamp.  To  obviate  frequent  renewal  the  first  Sawyer 
feeding-lamp  (Fig.  53)  was  devised. 

In  tliis  lamp  several  short  carbon  pencils  were  held  by 
copper  rods,  as  in  the  Konn  lamp,  and  as  fast  as  one 
was  consumed  or  disintegrated,  a  cam,  rotated  by  a 
coiled  spring,  forced  another  carbon  into  contact  with 
the  block  above.  Thus  a  very  durable  apparatus 
was  obtained,  but  by  no  means  a  successful  one ; 
for  when  the  lamp  is  properly  charged,  or  exhausted, 
chemical  change  in  the  carbon  is  no  longer  to  be  con- 
sidered, and  the  point  of  disintegration  is  generally  the 
upper  point  of  contact.  In  this  form  of  self -renewing 
device  we  do  not,  therefore,  obtain  the  full  value  of  the 
pencil,  which  ordinarily  drops  out  when  it  is  only  par- 
tially or  even  very  slightly  disintegrated. 

A  long  pencil,  fed  through  an  elastic  contact,  was  the 
originally-held  conception,  and  this  was  eventually  re- 
sorted to  in  the  lamp  (Fig.  54)  designed  early  in  the 
year  1879.  In  this  lamp,  by  means  of  an  electro-mag- 
netic switch,  an  electro-magnet,  operating  through  the 
glass  stopper  of  the  globe,  was  caused  to  feed  upward 
between  elastic  contacts,  as  fast  as  disintegration  oc- 


NEW  FORMS  OF  LAMPS. 


89 


cnrred,  a  long  carbon  pencil  travelling  in  a  metallic 
tube. 


Fig.  54.  Electro-Magnetic  Self-Renewing  Lamp. 


> f 

Fig.  55.  Hand-Feeder. 


Imperfections  in  the    operation   of    electro-magnetic 
feeding  devices  led  to  the  designing  of  another  lamp 


90  ELECTRIC  LIGHTING  BY  INCANDESCENCE. 

(Fig.  55),  in  which  the  pencil  was  fed  upward  from  the 
outside,  when  necessary,  or  drawn  downward  from  its. 
connection  with  the  upper  contact-rollers  when  extin- 
guishment of  the  light  was  desired.  With  lamps  of  this 
type  the  first  private  residence,  it  is  believed,  in  the 
world,  was  practically  illuminated  by  electricity  in  the 
winter  of  1879-80  and  during  the  following  month  of 
March.*  The  halls,  parlors,  and  upper  chambers  of  a 
New  York  dwelling-house  were  supplied  with  electrici- 
ty, through  a  single  conductor,  by  a  generator  located  a 
block  and  a  half  distant.  Each  light  was  turned  on  or 
off,  or  graduated  to  any  desired  degree  of  intensity,  in- 
dependently of  other  lights.  The  internal  resistance  of. 
each  lamp  was  about  .25  ohm.f 

*  No.  226  West  Fifty-fourth  Street,  New  York  City. 

f  Since  this  was  written  our  attention  has  been  called  to  the  fact  that  at 
Salem,  Mass.,  during  the  month  of  July,  1859,  Professor  Farmer  lighted  his 
parlor  by  two  incandescent  platinum  lamps.  In  a  letter  to  the  Salem  Ob- 
server of  November  2,  1878,  Professor  Farmer  adds:  ''And  this  electric 
light  was  subdivided,  too !  This  was  nineteen  years  ago,  and  it  was  un- 
doubtedly the  first  dwelling-house  ever  lighted  by  electricity.  A  galvanic 
battery  of  some  three  dozen  six-gallon  jars  was  placed  in  the  cellar  of  the 
house,  and  it  furnished  the  electric  current,  which  was  conveyed  by  suitable 
conducting-wires  to  the  mantelpiece  of  the  parlor.  Either  lamp  could  be 
lighted  at  pleasure,  or  both  at  once,  by  simply  turning  a  little  button  to  the 
right  for  a  light,  to  the  left  for  a  dark."  It  is  barely  possible  that  Professor 
Farmer's  memory  may  be  in  error  in  respect  of  dividing  the  current.  Whe- 
ther it  would  have  been  more  natural  for  him  to  divide  the  battery  into  two 
separate  parts  of  some  one  and  a  half  dozen  jars  each,  and  operate  one  lamp 
from  each  part,  than  to  go  to  the  trouble  of  arranging  resistances  and  com- 
plicated switches  in  order  to  operate  so  small  a  number  of  lamps  as  two 
from  a  single  battery  in  close  proximity  to  them,  is  not  considered;  but  it 
would  have  been  more  satisfactory  if,  in  making  the  above  claim,  Professor 
Farmer  had  stated  in  what  manner  a  button  was  arranged  so  as  to  light 
both  lamps  at  once,  or  to  light  either  one  separately,  by  the  one  operation  of 
turning  the  button  to  the  right. 


CHAPTER  VII. 

NEW  FOEMS   OF   LAMPS    (CONTINUED). 

"WE  may  now  be  supposed  to  have  arrived  at  an  ade- 
quate conception  of  the  principles  underlying 
the  various  forms  of  incandescent  lamps.  We  have 
seen  that  an  incandescent  carbon,  however  complete- 
ly isolated  from  gases  with  which  at  high  tempera- 
tures it  enters  into  chemical  combination,  is  a  destructi- 
ble mass  of  matter.  We  have,  perhaps,  reached  the 
conclusion  that  means  for  its  renewal  must  be  provided, 
and  that  this  renewal  must  not  be  frequent,  and  that  it 
must  be  cheaply  accomplished.  The  lamp,  furthermore, 
must  be  cheaply  and  hermetically  sealed,  and  readily  re- 
charged with  a  carbon-preservative  atmosphere,  or  ex- 
hausted of  such  atmosphere,  or  exhausted  of  atmos- 
pheric air. 

The  new  Sawyer  lamp,  exhibited  in  New  York,  and  at 
the  Franklin  Institute  in  Philadelphia  within  the  past 
few  weeks,  is  designed  to  meet  the  requirements  men- 
tioned. The  illustration  (Fig.  56)  shows  this  lamp  in  its 
perfected  form. 

In  Fig.  57  the  lamp  is  shown  with  the  interior  works 
and  base  apart  from  the  enclosing  globe.  Upon  a  thin 
metallic  base  is  fixed  one  of  the  upright  metallic  con- 
ductors leading  to  the  top  of  the  lamp.  The  other  con- 
ductor is  fixed  to  an  insulated  bolt  passing  downward 
through  the  centre  of  the  base.  These  conductors  are  of 


ELECTRIC  LIGHTING  BY  INCANDESCENCE. 


steel,  in  order  to  prevent  rapid  con- 
duction of  heat  to  the  base,  and  are 
formed  as  shown  in  order'  that  they 
may  be  readily  stamped  from  sheet- 
metal  and  pressed  into  the  requir- 
ed shape.  By  means  of  a  copper 
plunger  attached  to  a  wire  running 
over  a  winding-drum  at  the  base  of 
the  lamp,  in  which  drum  an  ordina- 
ry watch  spring,  furnishing  the  mo- 
tive power,  is  coiled,  a  long  pencil 
of  carbon  in  the  plunger-tube  is  au- 
tomatically fed  upward  through  the 
lower  elastic  carbon- contacts  to  a 
connection  with  the  upper  perforat- 
ed carbon-block.  Thus  the  pencil 
is  constantly  forced  to  a  bearing 
against  the  upper  carbon-block  un- 
til entirely  disintegrated  ;  and  when 
entire  disintegration  has  occurred  the 
plunger  closes  the  circuit  of  the  lamp. 
As  heretofore  explained,  the  point  at 
which  disintegration  mainly  takes 
place  is  the  upper  point  of  contact ; 
and  as,  when  the  pencil  is  protected 
from  combining  matter,  this  disinte- 
gration amounts  to  between  the  one- 
hundredth  and  the  fiftieth  part  of  an 
inch  for  every  hour  the  lamp  is  run, 
and  as  the  pencil  is  eight  inches  in 
length,  it  follows  that  the  useful 
lifetime  of  the  carbon  is  from  400  Fig" 56'  TheL^e4!cted  Sawyer 


NEW  FORMS  OF  LAMPS. 


93 


Fig.  57.  The  Sawyer  Lamp,  apart. 


94  ELECTRIC  LIGHTING  BY  INCANDESCENCE. 

to  800  hours,  equivalent  to  four  hours'  daily  use  for 
from  100  to  200  days.  In  this  calculation  it  is  assumed 
that  the  intensity  of  the  light  shall  not  exceed  that  of 
two  good  five-foot  gas-burners,  or  at  most  thirty  candle- 
power.  Run  at  a  higher  intensity  the  durability  of  the 
pencil  is  diminished. 

The  glass  globe  of  the  lamp  has  no  direct  connection 
with  the  base  supporting  the  lamp  mechanism.  In 'a 
thin,  spun-metal,  open  cup,  amounting  practically  to  a 
short  tube,  the  globe  is  sealed  by  heating  the  cup  and 
the  glass,  and  pouring  into  the  annular  space  between 
the  glass  and  cup  a  sealing  compound  which  is  elastic 
at  all  ordinary  temperatures,  adheres  to  both  glass 
and  metal,  and  does  not  soften  at  temperatures  at- 
tained in  the  lamp.  The  sealing  space  is  two  inches 
deep  and  one-quarter  inch  wide,  and  the  sealing  com- 
pound substantially  as  homogeneous  as  glass  ;  hence  the 
element  of  leakage  at  this  point  may  be  disregarded. 

In  order  to  place  the  carbon  pencil  in  the  lamp,  the 
upper  carbon-block  is  carried  to  one  side  by  moving  the 
sustaining-arm  on  the  standard  connected  with  the  insu- 
lated steel  upright,  and  space  is  made  for  the  pencil  by 
moving  the  plunger  to  the  bottom  of  the  tube  and  thus 
unwinding  the  wire  on  the  drum.  The  lower  carbon 
clamping-blocks,  whose  mutual  pressure  is  sustained  by 
a  spiral  spring,  placed  lower  down  in  the  lamp  so  as  to 
prevent  its  undue  heating,  are  then  separated,  and  the 
pencil  of  carbon  is  dropped  into  the  tube.  Finally,  the 
upper  carbon-block  is  moved  back  into  the  position 
shown,  when  the  lower  carbon-clamps  and  the  winding- 
drum  are  released,  and  the  pencil  is  brought  to  a  bearing 


NKW  FORMS  OF  LAMPS.  95 

in  a  central  opening  through  the  upper  carbon-block. 
The  circuit  is  by  way  of  an  insulated  wire  enclosed  in  the 
bracket  to  the  central  insulated  bolt,  one  of  the  upright 
steel  conductors,  and  the  upper  carbon-block  ;  and  down- 
ward, through  the  pencil,  as  far  as  the  lower  clamping- 
blocks,  and  the  other  upright  steel  conductor,  to  the  base 
of  the  lamp  and  the  bracket.  To  connect  a  lamp  in  cir- 
cuit it  is  therefore  necessary  to  fix  it  to  the  ordinary 
nipple-thread  of  a  gas-fixture,  the  two  contacts  thus 
being  established. 

The  peculiar  shaping  and  general  design  of  the  parts 
of  the  lamp  are  such  as  to  facilitate  and  chqapen  their 
manufacture.  The  carbon-blocks  are  formed  in  moulds. 
To  prevent  oxidization  from  handling  and  exposure,  all 
of  the  parts  are  nickel-plated.  All  of  the  metallic  parts 
above  the  upright  steel  conductors,  and  the  pencil-tube, 
are  of  pure  copper.  The  leading  wires  of  the  winding- 
drum  and  the  coiled  clamping-spring  are  of  steel.  All 
of  the  parts  at  the  base  of  the  lamp,  excepting  the 
screws,  are  of  brass.  A  stop-cock,  or  a  single  opening, 
through  the  base,  closed  by  a  short  brass  screw,  is  em- 
ployed in  the  charging  of  the  lamp. 

When  the  carbon  pencil  has  been  -introduced,  the 
glass  globe,  sealed  in  the  brass  spun  cup,  is  lowered 
over  the  works  and  fits  closely  to  the  shoulder  turned 
on  the  base.  The  workman  then  passes  a  soldering- 
tool  around  the  junction  of  the  cup  with  the  base,  and 
this  joint  is  hermetically  sealed.  To  facilitate  the  sol- 
dering, as  well  as  to  economize  material  and  prevent 
excessive  heating  of  the  sealing  compound  between  the 
globe  and  the  cup,  the  base  as  well  as  the  cup  is  made 


96 


ELECTRIC  LIGHTING  BY  INCANDESCENCE. 


only  thick  enough,  to  be  substantial.  To  renew  the 
penci],  when  entirely  destroyed,  the  junction  of  the  cup 
and  base  is  rotated  in  the  flame  of  a  Bunsen  burner, 
when  the  solder  softens  and  the  globe  and  cup  are  re- 
moved. To  replace  the  pencil,  and  resolder  the  connec 
tion  of  the  cup  and  base,  is  the  work  of  a  few  minutes. 
The  globe,  once  sealed  in  the  cup,  is  not  again  disturbed. 
At  each  renewal  of  the  carbon  it  is  of  course  necessary 
to  refill  the  globe  with  nitrogen,  the  stop-cock  or  screw, 
closing  the  charging  opening,  being  also  finally  soldered, 
in  order  to  ensure  hermetical  sealing  of  the  lamp 
throughout. 

All  insulations  above  the  base  are  of  mica,  in  order 
that  the  heat  of  the  upper  works  may  not  disengage 
dust  or  vapors,  whose  action  upon  the  incandescent  pen- 
cil would  be  deleterious.  The  diameter  of  the  globe  is 
2  inches  and  its  length  10  inches.  Lamps  have  been 
constructed  of  all  sizes  down  to  one  having  a  globe  % 
inch  in  diameter  and  2J  inches  in  length,  but  the  dimen- 
sions adopted  have  been  found  to 
be  the  best  in  practice.  The  shape 
or  design  of  the  globe  is  inconse- 
quential, which  may  also  be  said 
of  the  general  structure  of  the 
lamp,  except  in  so  far  as  questions 
of  economy  are  concerned. 

The  method  of  sealing  the  insu- 
lated central  bolt,  and  establish- 

Fig.  58.  Bracket-Connections. 

ing  the    external  connections   of 

the  lamp,  is  shown  in  Fig.  58,  in  which  A  is  the  arm  of 
any  gas-fixture,  and  B  the  base  of  the  lamp.     The  upright 


NEW  FORMS  OF  LAMPS. 


97 


conductor  L  is  fastened  to  the  bolt  I  by  a  screw,  M.  In 
a  conical  cavity  leading  to  the  long  bolt-hole  is  placed  a 
conical  fibre  washer,  J.  In  passing  through  this  hole  the 
bolt  does  not  touch  its  sides,  but  while  the  base  is  hot 
the  annular  space  around  the  bolt  is  filled  with  the  same 


Fig.  59.  Chandelier  of  Lamps. 

cement,  K,  as  is  employed  in  sealing  the  globe  to  its  cup, 
and  the  nut  G,  bearing  upon  the  conical  fibre  washer 
H,  is  firmly  screwed  upon  the  lower  end  of  the  bolt. 
The  cap  C  is  then  screwed  on  to  the  projection  from  the 
base.  In  a  cavity  in  the  end  of  the  bracket  is  sunk  an 
insulating  washer,  D,  through  which  passes  the  insulated 


98  ELECTRIC  LIGHTING  BY  INCANDESCENCE. 

wire  !N",  screwed  into  contact-nut  F.  The  coiled  spring 
E  gives  elasticity  to  the  lower  point  of  contact,  so  that 
the  lamp  may  be  turned  into  any  position.  The  long, 
narrow,  annular  space  around  the  bolt  I,  filled  with  ho- 
mogeneous cement  adhering  perfectly  to  the  metal,  en- 
sures the  hermetical  sealing  of  this  last  and  most  difficult 
joint  to  seal. 

In  Fig.  59  the  arrangement  of  a  chandelier  system  of 
lamps  is  illustrated. 

The  luminous  intensity  of  the  new  Sawyer  lamp,  which 
is  the  same,  under  like  circumstances,  as  that  of  all  the 
Sawyer- Man,  Konn,  Kosloff,  Bouliguine,  and  other  Saw- 
yer lamps,  is  from  two  to  three  ordinary  five-foot  gas- 
burners.  What  is  meant  by  this  is  the  intensity  of  light 
produced  at  which  it  is  considered  safe  to  run  the  lamp 
continuously,  when  it  is  desired  tliat  renewal  of  the  car- 
bon pencil  shall  not  be  necessary  more  frequently  than 
once  in  from  six  months  to  a  year.  Doing  two  hun- 
dred hours'  actual  work  the  lamp  may  be  run  at  an  in- 
tensity of  from  100  to  200  candles.  Doing  fifty  hours' 
work  it  may  be  run  at  an  intensity  of  from  200  to  600 
candles. 

Numerous  measurements  of  the  power  of  the  light 
have  been  made,  but  the  most  critical,  conducted  by 
Mr.  Edgerton,  with  a  Sugg  photometer,  accord  the  small- 
power  lamp  a  luminous  intensity  of  27.4  candles.* 


*  The  following  certificate  by  Mr.  Edgerton,  referring  to  the  perfected 
Sawyer-Man  lamp,  and  which  applies  as  well  to  all  pencil  lamps  in  which  a 
pencil  of  the  same  length  and  cross-section  is  rendered  incandescent,  con- 
tains some  valuable  suggestions  in  view  of  the  candle-power  claimed  by  gas 
corporations  and  that  shown  at  their  laboratories  : 


NEW  FORMS  OF  LAMPS.  99 

In  order  to  obtain,  when  desired,  greater  illuminating 
power,  a  larger  lamp  (Fig.  60)  has  been  devised. 

The  dimensions  of  this  lamp  are  4  X  16  inches,  and  its 
luminous  intensity  is  from  100  to  1,000  candles,  accord- 
ing to  the  length  of  pencil  brought  to  incandescence 
and  the  volume  of  current  supplied.  At  the  Franklin 
Institute,  in  Philadelphia,  on  November  9,  1880,  a 
single  large  lamp  served  to  illuminate  the  lecture-hall 
with  the  brilliancy  of  mid-day.  There  is  no  difference 
in  construction  between  this  lamp  and  the  small  lamp, 
excepting  that  in  the  large  lamp  the  upright  conduc- 
tors are  made  of  round  steel  rods,  which  is  sometimes 
true  of  the  small  lamps.  In  the  large  lamp  the  carbon 
pencil  is  12  inches  in  length  and  -^  of  an  inch  in  diame- 
ter, with  an  exposed  section  of  1^  inches ;  while  in  the 
small  lamp  it  is  TV  inch  in  diameter,  with  an  exposed  sec- 

NEW  YORK,  November  8,  1878. 

The  illuminating  power  of  one  of  the  Sawyer-Man  lajnps,  tested  by  me 
this  day,  gave,  in  comparison  with  a  standard  sixteen-candle  burner,  a  power 
of  1.714  burners,  or  27.42  standard  sperm  candles. 

(Signed)  H.  H.  EDGERTON. 

In  order  to  compare  the  light  with  that  afforded  by  ordinary  gas-burners, 
the  different  burners  in  ordinary  use,  with  coal  gas,  may  be  rated  about  as 
follows,  for  a  rate  of  five  cubic  feet  per  hour  consumption  : 

Ordinary  fish-tail,  Scotch  tip,  about  5  candles. 

Young  America,  brass  fish-tail,  8  candles. 

Gleason,  noiseless  Argand,  1 1  candles. 

Lava  tip  (excavated  head),  12  to  13  candles. 

A  very  large  flame,  burning  at  a  rate  of  8  or  9  cubic  feet,  will  give  a  pro- 
rata  light  of  about  15  candles  for  5  cubic  feet. 

The  above  is  based  upon  gas  made  from  ordinary  Pittsburgh  coal.  Mix- 
tures of  cannel  or  naphtha  improve  the  quality  according  to  the  amount 
used.  (Signed)  H.  H.  EDGERTON. 

London  is  supplied  with  gas  of  16  candle-power  per  5-foot  burner.  The 
Liverpool  street-lamps  give  a  light  at  the  rate  of  16  candles  per  5  cubic  feet 
with  4  cubic  feet  consumption. 


100 


Fig.  GO.  Large  Sawyer  Lamp. 


NEW  FORMS  OF  LAMPS.  1()1 

tion  of  f  inch.  Owing  to  the  greater  intensity  at  which, 
the  large  lamp  is  run,  the  working  duration  of  the  pen- 
cil, when  the  globe  is  perfectly  charged  with  nitrogen,  is 
about  200  hours.  The  cost  of  renewal  (that  of  the  car- 
bon and  nitrogen  elements)  is  largely  in  excess  of  the 
cost  of  renewal  in  the  small  lamps,  and  varies  from  25  to 
30  cents  per  lamp. 

The  permanent,  elastic  closing  of  the  Sawyer  globe  in 
its  metallic  containing-cup  is  the  only  method  yet  de- 
vised that  affords  the  necessary  hermetical  sealing,  ex- 
cepting that  of  Geissler,  which  is  employed  by  Mr.  Edi- 
son. Many  experimentalists  in  this  line  have  employed 
hydraulic  joints:  Kosloff  employed  a  bath  of  olive-oil 
around  the  joints ;  Guest  and  others  have  employed 
quicksilver ;  our  own  experiments,  of  a  similar  charac- 
ter, have  been  confined  to  viscous  hydrocarbons.  But  all 
these  devices  are  inadequate  ;  for  while  they  may  truly 
prevent  the  entrance  of  air,  in-leakage  of  the  mobile  seal- 
ing substance  itself  cannot  te  prevented,  and  thus  there 
is  introduced  into  the  lamp  an  element  which  will  either 
destroy  the  carbon  or  so  blacken  the  globe  as  to  obscure 
the  light.  Every  part  of  the  lamp  must  be  perfectly 
clean ;  and,  indeed,  the  delicacy  of  manipulation  neces- 
sary in  the  construction  of  incandescent  lamps  cannot  be 
appreciated  by  any  one  not  familiar  with  the  subject, 
and  who  only  observes  the  facility  with  which  the  skilled 
workman  performs  his  duties. 

Operating  upon  the  principle  of  decomposition  of  hy- 
drocarbon and  the  deposit  of  the  carbon  atom  upon  an 
incandescent  filament,  we  have  constructed  an  open-air 
lamp  of  a  somewhat  novel  description  (Fig.  61). 


102 


ELECTRIC  LIGHTING  BY  INCANDESCENCE. 


Upon  a  brass  wheel  are  mounted  six  carbon  horse- 
shoes, all  the  negative  poles  of  which  are  connected  to- 
gether on  the  wheel,  and  the  positive  poles  of  each  op- 


Fig.  61.  The  Sawyer  Open-Air  Lamp. 


posite  pair  of  which  are  connected  together  and  to 
opposite  segments  of  a  commutator  of  six  segments. 
The  current  is  directed  by  a  contact-brush  and  the  frame- 
work of  the  apparatus,  and,  dividing,  passes  through 
the  uppermost  and  lowermost  carbons  at  the  same  time. 


NEW  FORMS  OF  LAMPS.  103 

The  uppermost  carbon  burns  in  the  air  at  intense  incan- 
descence, while  the  lowermost  carbon,  immersed  in  oil 
in  a  suitable  containing  vessel,  becomes  coated  with  de- 
posit carbon.  As  the  uppermost  carbon  consumes  and 
decreases  in  size  the  intensity  of  the  light  does  not  in- 
crease, for  the  increase  in  the  size  of  the  lowermost  car- 
bon balances  the  effect  of  the  current  above  by  increas- 
ing the  supply  below  and  decreasing  the  supply  above. 
By  means  of  intermittently-operating  clock-work,  before 
disruption  of  the  uppermost  carbon  occurs,  the  next  pair 
of  carbons  is  brought  into  position  ;  and  the  operations 
described  continuing,  there  is  presented  the  anomaly  of 
an  incandescent  open-air  lamp  of  indefinite  duration,  in 
which,  by  one  operation,  light  is  produced  and  carbon 
manufactured,  so  long  as  the  supply  of  oil  is  main- 
tained. The  objection  to  this  lamp  is  that  one-half  of 
the  current  is  always  employed  in  renewing  wasted 
carbon. 

Light  by  incandescence  is  considerably  more  costly 
than  light  by  the  voltaic  arc,  when  the  volume  of  light 
obtainable  is  the  sole  consideration.  The  same  expendi- 
ture of  power  that  will  produce  a  light  of  1,000  candles 
by  the  voltaic  arc  will  not  produce,  on  the  average,  more 
than  one-half  or  one-third  as  much  light  by  incan- 
descence in  a  divided  circuit.  It  should  not,  however, 
be  forgotten  that  the  power  of  any  light  decreases  as  the 
square  of  the  distance  from  it,  and  that  one- fourth  of  the 
light  of  the  arc  distributed  at  four  or  five  appropriate 
points,  thus  reducing  the  power  of  each  light  to  one- 
sixteenth  of  that  of  the  voltaic  arc,  will  give  substan- 
tially as  good  a  general  illumination  as  the  voltaic  arc. 


104  ELECTRIC  LIGHTING  BY  INCANDESCENCE. 

The  incandescent  light  is  whatever  may  be  desired. 
The  voltaic-arc  light  is  necessarily  a  powerful  one.  The 
objection  to  it,  if  used  without  a  shade,  is  its  great  in- 
tensity and  ghastly  effects,  and  in  order  to  obviate  these 
defects  glass  shades  of  more  or  less  opacity  are  em- 
ployed, which,  according  to  practical  tests,  involve  a 
wastage  in  light  of- 

With  ground  glass,  30  per  cent.  ; 

With  thin  opal  glass,  40  per  cent.  ; 

With  thick  opal  glass,  60  per  cent. 

In  some  cases  the  wastage  is  nearly,  if  not  quite,  75  per 
cent. 

The  loss  of  light  involved  in  the  "toning  down"  of 
the  arc  is  clearly  set  forth  in  confirmed  tests  of  the 
power  of  the  Jablochkoff  candle,  now  extensively  used 
in  England  and  France.  The  actual  power  of  this  light 
is  453  standard  candles,  but  owing  to  obscuration,  occa- 
sioned by  the  opalescent  globes  with  which  it  is  neces- 
sary to  surround  the  light,  it  is  found  that  only  43  per 
cent,  of  its  full  power  is  available.  In  incandescent 
lighting  no  such  loss  occurs,  and  the  cost  of  the  carbon 
consumed,  which  in  voltaic-arc  lamps  amounts  to  from 
four  to  six  cents  per  hour  per  2,000  candles'  light,  is  re- 
duced to  an  inconsequential  figure. 

In  concluding  this  chapter,  it  is  proper  to  remark  that 
the  light  of  an  incandescent  carbon  is  very  unlike  that 
of  the  voltaic  arc.  Its  characteristics  are  the  character- 
istics of  daylight ;  and  this  is  true  to  such  an  extent 
that,  from  its  soft  and  agreeable  nature  and  absence  of 
glaring  effects,  the  degree  of  illumination  afforded  is  not 
always  readily  appreciated. 


CHAPTER  VIII. 

PRESERVATION    OF  INCANDESCENT   CARBONS. 

TN    isolating    the   carbon  conductor  from   deleterious 
gases  we  have  the  choice  of  three  distinct  processes  : 

1.  Exhausting  the  globe  of  air  ; 

2.  Filling  the  globe  with  nitrogen  ; 

3.  Filling  the  globe  with  nitrogen,  hydrogen,  or  hy- 
drocarbon gas,  and  exhausting. 

In  all  cases  the  interior  surface  of  the  globes  and  the 
works  of  the  lamp  enclosed  must  be  absolutely  dry,  for 
the  presence  of  moisture  means  the  presence  of  the  ox- 
ide of  hydrogen,  whose  speedy  decomposition  sets  free 
the  destructive  oxygen  atom.  Various  methods  of  arti- 
ficial drying  have  been  devised,  very  few  of  which  are 
serviceable  here.  The  calcium  chloride  is  not  only  an 
imperfect  drying  agent,  but  has  been  found  to  work  in 
some  manner  injuriously ;  and  the  same  is  true,  as  to 
the  first  part,  of  concentrated  sulphuric  acid  in  its  pur- 
est form.  The  degree  of  dry  ness  necessary  is  one,  in 
practical  operation,  beyond  the  capacity  of  these  chemi- 
cals. Anhydrous  sulphuric  acid  is  not  only  dangerous 
to  handle,  but  injurious  to  the  works  of  the  lamp,  and 
should  never  be  used.  The  only  suitable  agent  at  pre- 
sent known  is  the  phosphoric  anhydride,  which  must  be 
chemically  pure  and  is  not  imported  in  this  country. 
We  have  procured  considerable  quantities  direct  from 

105 


106  ELECTRIC  LIGHTING  BY  INCANDESCENCE. 

the  manufacturers  in  Germany  ;  as  used  by  Mr.  Edison, 
it  is  prepared  by  himself  by  the  combustion  of  phos- 
phorus in  a  large  containing  vessel,  to  which  air  is  slowly 
admitted.  The  resultant  vapor  is  condensed  upon  the 
sides  of  the  vessel,  which  is  funnel-shaped  at  the  bot- 
tom, and  collected  in  a  glass  receiver  below. 

Protracted  tests  of  many  kinds  of  lamps  show  that  in 
a  perfect  vacuum  as  to  oxygen,  and  in  an  absolutely  pure 
atmosphere  of  nitrogen,  there  is  no  consumption  of  the 
carbon,  which  stands  sharp  and  clear,  except  as  to  gra- 
dual decay  of  structure,  so  long  as  the  volume  of  cur- 
rent supplied  is  not  too  great. 

From  disintegration,  more  or  less  rapid,  the  carbon 
cannot  be  protected.  It  has  been  supposed  that  the  en- 
tire absence  of  any  atmosphere  is  more  conducive  to  lon- 
gevity of  the  incandescent  conductor  than  the  presence 
of  an  atmosphere  with  which  it  cannot  enter  into  chemi- 
cal combination,  because  in  the  latter  case  there  exists 
in  the  lamp  a  constant  circulation  of  currents  of  the 
gas,  due  to  the  heat  evolved,  which  may  be  supposed  to 
' c  wash ' '  the  carbon,  and,  by  some  process  of  reasoning, 
to  waste  it  away.  If  carbon,  heated  to  incandescence, 
usually  became  a  soft,  unstable  mass,  instead  of  the 
hard,  dense  body  it  is,  there  might  be  some  foundation 
for  this  idea,  which  perhaps  originated  from  observa- 
tions of  that  form  of  disintegration  in  which  extremely 
thin,  feathery  flakes  are  disengaged  and  float  away. 
Their  disengagement  occurs  equally  in  nitrogen  and  in 
vacuo,  with  this  difference  :  that  in  nitrogen  they  are  car- 
ried upward  and  around  by  the  currents  of  heated  gas, 
and  in  vacuo  they  fall  to  the  base  of  the  lamp. 


PRESERVATION  OP  INCANDESCENT  CARBONS.          107 

The  preparation  of  nitrogen  sufficiently  pure  for  the 
purposes  of  incandescent  lighting  is  ordinarily  an  ex- 
tremely delicate  laboratory  process.  Prepared  by  the 
burning  of  phosphorus  in  a  closed  air-chamber,  it  is  ut- 
terly inadequate ;  for,  however  carefully  its  subsequent 
manipulations  may  be  conducted,  there  are  present  at 
the  outset  too  many  elements  of  impurity,  and  a  trace  of 
phosphorus  always  remains. 

The  best  method  of  obtaining  nitrogen  that  we  have 
employed  is  that  of  Prof.  Stillman.  Solutions  of  ammo- 
nic  chloride  and  potassic  nitrite  are  heated  in  a  glass  re- 
tort. The  vapor-gaseous  product,  consisting  of  nitrogen, 
water,  ammonia,  and  nitric  oxide  (although  the  reaction 
given  in  the  text-books  is  KNO2  +  JSTH4CL  =  KCL  + 
N2  +  2H2O),  is  passed  successively  through  the  conden- 
ser ;  sulphuric  acid  (to  remove  excess  of  water),  and  so- 
lutions of  iron,  caustic  potassa,  and  pyrogallic  acid 
mixed  with  caustic  potassa,  in  Wolff's  bottles  ;  and  then 
through  long  tubes  filled  with  pumice-stone  in  pieces, 
moistened  with  sulphuric  acid.  Finally,  the  gas  is 
passed  through  tubes  containing  phosphoric  anhydride, 
and  a  combustion-tube  containing  melted  sodium,  to  re- 
move the  last  trace  of  oxygen,  oxidized  particles  of  which 
are  prevented  from  coming  over  by  means  of  Wolff's 
bottles  filled  with  cotton.  The  gas  is  stored  in  tanks,  or 
in  strong  iron  reservoirs  under  pressure.  Thus  prepared 
the  cost  of  the  nitrogen  is  about  ten  cents  per  gallon. 

In  filling  a  globe  the  simplest  process  is  that  of 
"  washing  out,"  illustrated  in  Fig.  62,  in  which  several 
lamps  are  connected  in  series,  and  a  divided  circuit.  The 
gas  passes  from  a  receiver  through  a  purifier  consisting 


108  ELECTRIC  LIGHTING  BY  INCANDESCENCE. 

of  drying  apparatus  and  a  sodium  tube,  and  thence 
through  the  lamps  F  seriatim,  the  first  flow  of  gas  being 
wasted,  and  the  remainder  collected  in  a  second  receiver, 
from  which,  when  filled,  it  is  passed  back  directly  into 
the  first  receiver  by  means  of  a  connecting-tube  ;  and 
then  again  passes  through  the  purifier  and  the  lamps. 
As  every  gas  acts  as  a  vacuum  towards  every  other  gas, 


Fig.  62.  Nitrogen  Process. 

the  lamps  become  ultimately  filled  with  pure  nitrogen. 
In  order  to  expel  occluded  air,  it  is  useful  to  succes- 
sively heat  and  cool  the  carbons  while  the  nitrogen  is 
flowing.  By  closing  and  subsequently  soldering  the 
stop-cocks,  the  hermetical  sealing  of  the  lamps  is  ef- 
fected. 

Exhaustion  of  air  has  been  reduced,  by  means  of  the 
Sprengel  pump,  to  a  degree  heretofore  thought  unat- 
tainable. In  the  manufacture  of  the  Edison  lamp,  the 


PRESERVATION  OF  INCANDESCENT  CARBONS. 


109 


method  of  exhaustion  illustrated  in  Fig.  63  is  employed. 
A  is  a  Sprengel  pump,  B  a  drying-tube  of  phosphoric 


Fig.  63.  Edison  Exhaustion. 


110 


ELECTRIC  LIGHTING  BY  INCANDESCENCE. 


anhydride,  and  C  the  lamp  to  be  exhausted.  The  time 
required  to  obtain  a  nearly  perfect  vacuum  in  the  lamp 
is  from  ten  to  twenty  hours,  for  the  operation  of  the 
Sprengel  apparatus  is  extremely  slow.  The  degree  of 


Fig.  64.  Sawyer  Nitrogen  Exhaustion. 


exhaustion  ordinarily  attained  is  supposed  to  be  about 
the  one-millionth  of  an  atmosphere. 

In  order  to  improve  and  facilitate  the  process  of  iso- 
lating the  carbon,  the  apparatus  shown  in  Fig.  64  is  em- 


PRESERVATION  OF  INCANDESCENT  CARBONS. 

ployed  in  the  manufacture  of  the  Sawyer  lamp.  A  is  a 
reservoir  of  pure  nitrogen  under  pressure  ;  B,  the  drying- 
tube  of  phosphoric  anhydride ;  C,  Sprengel  pump ;  D, 
ordinary  air-pump ;  and  E,  the  lamp  or  series  of  lamps 
to  be  exhausted.  The  greater  portion  of  the  air  is  first 
rapidly  removed  by  means  of  the  machine  pump  D, 
when  the  stop-cock  connecting  it  is  closed,  and  that 
connecting  the  Sprengel  pump  is  opened.  By  this  ar- 
rangement the  slowly-acting  Sprengel  pump  has  only  a 
fraction  of  the  whole  work  to  do.  As  soon  as  the  de- 
gree of  exhaustion  equals  the  one-hundred-thousandth 
part  of  an  atmosphere,  which  is  but  one-tenth  as  high  as 
that  of  the  Edison  lamp  and  is  quickly  accomplished,, 
the  exhausting  process  is  stopped,  and  the  reservoir  stop- 
cock being  opened,  the  globe  is  filled  with  nitrogen. 
The  reservoir  is  then  shut  off,  and  pumps  D  and  C  are 
used  as  before,  until  the  vacuum  again  reaches  the  one- 
hundred-thousandth  part  of  an  atmosphere.  The  stop- 
cock of  the  lamp,  shown  in  the  lower  figure,  connected 
by  a  rubber  tube  which  is  prevented  from  collapsing  by 
an  enclosed  spiral  spring,  is  then  closed  by  driving  in 
the  small  tapering  pin  while  the  tube  is  still  connected, 
and  subsequently  soldering.  The  proportion  of  air  re- 
maining in  the  lamp  is,  therefore,  the  one-hundred- 
thousandth  part  of  the  one  hundred- thousandth  part,  or 
the  one- ten-billionth  part  of  an  atmosphere,  a  degree  of 
perfection  as  readily  obtained  as  an  exhaustion  of  .00001 
by  other  means. 

Filling  and  exhausting  with  hydrogen  and  hydrocar- 
bon gases  operate  to  similarly  reduce  the  quantity  of 
oxygen  present  in  the  lamp,  but  nitrogen  is  preferable 


112 


ELECTRIC  LIGHTING  BY  INCANDESCENCE. 


on   account    of    its  greater    freedom  from  impurities. 
When,  however,  the  hydrogen  or  the  hydrocarbon  gas 


ir 


m 


Fig.  65.  Carbons. 


is  absolutely  pure,  it  may  be  used  with  equal  advantage, 
and  in  some  cases  is  perhaps  more  readily  obtainable  in 
the  pure  state  than  nitrogen. 

In  the  plate  (Fig.  65)  the  behavior  of  carbon  under  va- 


PRESERVATION  OF  INCANDESCENT  CARBONS.          H3 

rying  conditions  is  shown,  but  the  difficulty  of  transfer- 
ring the  observations  of  the  eye  to  the  engraver's  block 
necessarily  renders  their  illustration  imperfect.  In  Fig. 
1  we  have  a  perfect  pencil,  sealed  in  a  substantially  per- 
fect atmosphere  or  vacuum. 

In  the  pencil  Fig.  2  is  shown  a  cavity  forming ;  elon- 
gating, as  in  Fig.  3 ;  and  finally  resulting  in  frac- 
ture, as  shown  in  Fig.  4.  This  occurs  in  a  lamp  where 
combustion  is  obviated,  and  would  seem  to  be  due  to  some 
metallic  particle  which  forms  a  carbide,  slowly  extend- 
ing through  the  mass  of  the  pencil.  In  Fig.  5  we  have 
the  ordinary  rupture,  for  which  there  may  be  any  one  of 
several  explanations  :  the  presence  of  an  impurity,  as  al- 
ready described  ;  a  minute  crack  in  the  pencil,  at  which 
the  current  concentrates  ;  or  possible  lateral  strain  acting 
upon  a  point  of  weakness.  The  effect  attempted  to  be 
illustrated  in  Fig.  6,  in  which  the  pencil  is  literally 
burst,  has  been  observed  but  once  in  our  experience,  and 
this  was  when  the  dynamo-electric  machine  was  acci- 
dentally short-circuited  for  an  instant,  accumulating  an 
intense  magnetic  field,  which  resulted  in  a  sudden  dis- 
charge of  current  of  great  power  upon  removal  of  the 
cause  of  the  short  circuit.  The  flaking- off  of  light,  fea- 
thery-shaped particles  of  carbon,  without  combustion, 
generally  from  the  central  and  upper  part  of  the  pencil, 
is  represented  in  Fig.  7.  Disintegration  of  the  points 
of  contact  of  the  pencil,  when  it  is  enclosed  in  an  atmos- 
phere of  pure  nitrogen,  is  well  illustrated  in  Fig.  8. 
In  Fig.  9  the  pencil  is  shown  slowly  consuming,  in  an 
atmosphere  containing  some  oxygen,  the  wastage  being 
.greatest  at  the  top  and  the  pencil  tapering  downward  to 


114  ELECTRIC  LIGHTING  BY  INCANDESCENCE. 

its  full  size,  due  to  the  difference  in  temperature  of  dif- 
ferent parts  of  the  pencil.  Fig.  10  shows  the  pencil  con- 
suming and  diminishing  uniformly  in  section,  as  in  air 
or  a  full  supply  of  oxygen,  until,  if  there  is  any  pres- 
sure brought  to  bear,  it  softens  and  bends  as  shown 
in  Fig.  11.  Fig.  12  represents  a  perfect  Sawyer-Man 
loop,  and  Fig.  13  a  loop  fractured.  In  Fig.  14  the 
loop,  diminishing  in  section  at  points  but  otherwise 
perfect,  is  well  represented.  Bending  of  the  loop  from 
heat,  as  in  Fig.  15,  occurs  only  when  at  different 
points  the  carbon  is  reduced  to  a  mere  filament  and  an 
arc  is  upon  the  point  of  forming.  Long  pencils  held 
with  connectors,  one  in  each  hand,  and  subjected  in  the 
air  to  extremely  powerful  currents,  have  frequently  been 
bent  into  peculiar  shapes,  one  of  which  is  illustrated  in 
Fig.  16. 

In  Fig.  17  we  have  a  striking  example  of  the  in- 
tensity of  the  heat  of  an  incandescent  carbon.  Owing 
to  disintegration  of  the  upper  point  of  contact,  one  of 
the  short  Sawyer-Man  pencils,  losing  its  support  while 
at  limpid  incandescence,  was  projected  against  the  side 
of  the  globe,  through  which  it  instantly  passed  as 
though  the  glass,  which  was  one- twelfth  of  an  inch  in 
thickness,  had  been  so  much  tissue-paper,  fusing  its  way 
slightly  downward,  and  finally  settling  in  the  position 
shown,  sealed  in  the  glass  as  perfectly  as  a  platinum 
wire  is  sealed  in  a  Geissler  tube.* 

*  A  section  of  the  globe  containing  this  pencil  was,  we  believe,  at  one 
time  in  the  hands  of  Mr.  Hopkins,  of  the  Scientific  American. 


CHAPTER  IX. 

DIVISION   OF   CUKRENT   AND    LIGHT. 

Ill" UGH  has  been  written  concerning  the  loss  of  light  by 
subdivision  of  the  current,  and  this  has  been  vari- 
ously estimated,  sometimes  as  the  square  and  sometimes 
as  the  cube  of  the  number  of  lights  among  which  the 
current  is  divided.  Upon  what  data  and  with  what  pur- 
pose these  estimates -have  been  made  it  is  difficult  to 
conceive,  for  they  have  no  foundation  in  practical  fact. 

If  to  the  conducting  pipe  of  a  gas  system  a  given  vol- 
ume of  illuminating  gas  is  supplied  in  a  given  time,  and 
all  this  gas  is  consumed  in  a  single  burner  in  order  to 
yield  a  given  light,  when  we  divide  the  volume  of  gas 
thus  supplied  among  two  or  more  burners  the  total  light 
produced  may,  indeed,  have  greatly  decreased.  We  do 
not,  however,  supply  gas  in  this  manner,  but  the  volume 
of  gas  supplied  is  in  direct  proportion  to  the  number  of 
burners  to  be  fed. 

What  is  true  of  gas  is  equally  true  of  electricity.  If 
a  fixed  volume  of  current,  sufficient  for  one  light,  is  fur- 
nished to  a  single  lamp  the  maxim  am  effect  is  produced, 
and  if  we  divide  this  fixed  volume  among  two  or  more 
lamps  the  total  effect  is  greatly  diminished ;  but  to  sup- 
pose that  such  a  division  is  contemplated  is  to  suppose 
a  similar  operation  in  the  case  of  gas,  and  criticism  of 
statements  based  upon  such  a  supposition  is,  simply, 

115 


ELECTRIC  LIGHTING  BY  INCANDESCENCE. 

waste  of  time  and  labor.  When  we  increase  the  num- 
ber of  lights  in  circuit,  we  increase  the  volume  of  cur- 
rent in  proportion ;  and  the  power  of  the  total  light  is 
increased  in  proportion ;  and  the  energy  expended  in 
producing  the  light,  and  therefore  its  cost,  is  increased 
in  proportion. 

Without  at  this  time  entering  into  any  considerations 
of  the  fact  that  the  current  from  a  single  generator  of 
electricity  has  repeatedly  been  divided  between  from  two 
to  two  hundred  incandescent  burners,  the  operations  of 
the  Brush  system  of  voltaic-arc  lighting  set  at  rest  the 
question  of  economical  subdivision. 

Two  machines  of  the  Brush  type  are  selected  for  com- 
parison— viz.,  the  six-light  and  the  sixteen-light  ma- 
chines, both  of  which  are  in  practical  use  throughout  the 
United  States — the  light  of  each  of  the  twenty -two  lamps 
being  of  the  same  intensity  as  that  of  each  and  every 
other  lamp. 

With  the  six-light  machine  the  total  driving  power 
absorbed  per  minute  is  236,940  foot-pounds,  or  39,490 
foot-pounds  per  lamp. 

With  the  sixteen-light  machine  the  total  driving  power 
absorbed  is  618,090  foot-pounds,  or  38,630  foot-pounds 
per  lamp.  4 

It  is  thus  clearly  shown  that  for  each  lamp  added  to 
the  circuit  there  is  an  expenditure  of  power  in  j  >ropor- 
tion  to  the  additional  work,  the  somewhat  diminished 
power  per  lamp  expended  in  the  sixteen-light  machine 
being  mainly  due  to  the  element  of  friction,  in  which 
the  percentage  of  absorption  of  power  is  less  in  large 
than  in  small  generators. 


DIVISION  OF  CURRENT  AND  LIGHT.  H7 

As  a  matter  of  fact,  there  is  no  limit  to  the  divisibility 
of  the  electric  current.  While  the  possibility  and  the 
impossibility  of  its  divisibility  become  from  time  to  time 
the  subject  of  controversial  discussion,  practical  subdi- 
vision is  a  daily  concomitant  of  every  telegraphic  circuit. 
Even  in  telephonic  transmission  the  current  generated  is 
divided  between  the  transmitter  and  the  receiving  instru- 
ment, and  in  some  large  telegraphic  stations  the  wires 
radiate  from  a  single  generator  in  several  directions,  and 
in  the  circuit  of  each  of  these  wires,  at  towns  and  cities 
along  their  route,  there  is  placed  a  greater  or  less  num- 
ber of  instruments,  each  of  which  is  energized  from  the 
source  common  to  all  of  them ;  and  the  proportion  of 
current  supplied  to  each  instrument  is  made  substan- 
tially the  same  in  all  cases  by  making  the  resistance  of 
the  instruments  uniform.  The  strength  of  the  current 
thus  supplied  is,  of  course,  inadequate  to  the  operation 
of  an  electric-lighting  system,  as  an  ordinary  main-line 
telegraphic  battery  is  inadequate  to  the  operation  of 
even  a  single  voltaic-arc  lamp;  but  if  we  increase  its 
strength  proportionately,  and  for  each  telegraphic  in- 
strument substitute  an  electric  lamp,  we  as  certainly  ac- 
complish subdivision  of  the  electric -light  current  as  sub- 
division of  less  powerful  currents  is  accomplished  with 
telegraphic  instruments.  Indeed,  the  laws  which  govern 
the  supply  of  gas  to  gas-burners  and  the  supply  of 
electricity  to  electric  burners  are  daily  recognized  and 
availed  of  in  the  operation  of  telegraphic  circuits. 

For  instance,  in  operating  a  given  number  of  tele- 
graphic instruments  in  series,  we  employ  a  given  num- 
ber of  cells  of  battery.  Suppose,  now,  that  we  double 


118  ELECTRIC  LIGHTING  BY  INCANDESCENCE. 

the  number  of  instruments  and  the  resistance  of  the  cir- 
cuit ;  all  the  instruments,  since  they  receive  proportion- 
ately less  current,  become  practically  inoperative,  and 
we  increase  the  number  of  cells,  and  therefore  the 
electro-motive  force  of  the  battery,  in  proportion  to 
the  additional  work  .required,  which  is  that  of  overcom- 
ing the  added  resistance.  If,  on  the  other  hand,  we 
divide  the  current  from  a  single  generator  among  two  or 
more  lines,  each  including  a  number  of  instruments  in 
series,  we  require  a  current  of  greater  quantity ;  hence 
we  increase  the  size  of  the  elements  of  the  generator. 

In  electric  lighting  there  are  five  methods  of  dividing 
the  current  from  a  single  generator  of  electricity : 

1.  The  series  system.     Passing  the  current  seriatim 
through  the  lamps,  as  in  the  Brush  system  of  lighting. 

2.  The  multiple  system.     Connecting  the  poles  of  the 
generator  with  two  parallel  wires,  and  placing  each  lamp 
in  a  branch  running  from  wire  to  wire,  as  in  the  Edison 
and  Maxim  systems. 

3.  The  multiple- series  system.     Connecting  the  poles 
of  the  generator  with  two  parallel  wires,  and  placing  a 
number  of  lamps  in  each  branch  running  from  wire  to 
wire,  as  in  the  Sawyer-Man  system. 

4.  The  series-multiple  system.     Connecting  one  pole  of 
the  generator  to  a  wire  which,  at  the  point  at  which  light 
is  needed,  divides  into  a  number  of  strands,  each  contain- 
ing a  lamp  or  lamps,  and  which  strands  again  combine 
together  in  a  single  wire,  which  runs  to  the  next  point  of 
division  ;  and  so  on  indefinitely,  returning  finally  to  the 
other  pole  of  the  generator ;  as  in  the  Sawyer  system. 

5.  The  secondary  system.     Passing  the  main  current 


DIVISION  OF  CURRENT  AND  LIGHT.  H9 

through  the  primary  wire  of  an  induction-c*oil,  in  the 
circuit  of  the  secondary  coil  of  which  the  lamp  is  placed 

(Fig.  66). 


Fig.  66.  The  Secondary  System. 

Alternating  or  intermittent  currents  are  employed,  and, 
owing  to  the  reactive  earth  inductions,  this  principle  can- 
not be  applied  over  any  considerable  territory.  More- 
over, it  involves  loss  of  power  in  the  heating  of  the  iron 
core  of  the  induction  apparatus,  is  an  indirect  applica- 
tion of  power,  and,  in  electric  as  in  all  other  forces,  di- 
rect application  is  found  to  be  the  most  economical.* 

How  to  practically  divide  the  current  from  a  single 
source  among  a  large  number  of  incandescent  lamps  has 
been  considered  a  debatable  question.  We  shall  content 
ourselves  with  glancing  at  the  results  which  must  follow 
an  extension  of  the  four  systems  which  appear  to  be 

*  As  recently  as  1877-78  several  claimants  to  this  method  of  subdivision 
have  appeared,  but  the  system  was  patented  in  England  by  Harrison  in  1857 
(Letters-Patent  588),  under  the  title,  "Improvements  in  obtaining  Light  by 
Electricity,"  and  it  is  not  quite  clear  that  Harrison  was  the  original  in- 
ventor. The  Harrison  patent  expired  in  1871,  unless  the  Government  taxes 
were  unpaid,  in  which  case  it  must  have  expired  at  an  earlier  date. 


120  ELECTRIC  LIGHTING  BY  INCANDESCENCE. 

suitable,  assuming  that  in  each  case  1,000  lamps  and 
10,000  lamps  are  to  be  operated  upon  a  single  circuit. 
Where  there  is  a  limited  number  of  lamps  either  the 
series,  the  multiple,  the  multiple-series,  or  the  series- 
multiple  systems  may  be  employed  with  about  equal  ad- 
vantage ;  but  where  the  number  of  lamps  is  increased  to 
hundreds  or  thousands,  as  must  be  the  case  in  any  gene- 
ral application  of  electric  lighting,  considerations  novel 
in  character  rapidly  present  themselves. 

Taking  h'rst  the  series  system  (Fig.  67),  in  which  the 

© © 

Fig.  67.  Lamps  in  Series. 

current  traverses  the  lamps  seriatim,  and  assuming  that 
interruption  of  the  circuit  of  any  lamp  will  not  interrupt 
the  entire  circuit,  we  have  with  1,000  lamps  a  resistance, 
not  including  the  internal  resistance  of  the  generator  or 
the  external  resistance  of  the  main  conductor,  of  1,000 
ohms.  With  10,000  lamps  the  resistance  becomes  10,000 
ohms. 

Can  this  resistance  be  overcome  by  any  practicable 
construction  of  generator? 

The  electro-motive  force  of  current  necessary  to  ope- 
rate an  incandescent  lamp  of  one  ohm  resistance  is,  as  to 
the  lamp,  such  as  will  yield  a  voltaic  arc  -£%  of  an  inch 
in  length.  The  electro-motive  force  necessary  to  over- 
come the  resistance  of  1,000  lamps  is,  therefore,  that 
which  will  yield  an  arc  31J  inches  in  length,  or  with 
10,000  lamps  an  arc  26  feet  in  length. 

Assuming  its  existence,  we  need  not  describe  the  pro- 


DIVISION  OF  CURRENT  AND  LIGHT.  121 

bable  effect  of  a  current  of  such  tension  upon  the  person 
of  any  one  unfortunate  enough  to  come  in  contact  with 
the  conductor,  or  the  difficulty  of  insulating  the  con- 
ductor at  all ;  but  will  simply  say  that  no  generator  could 
be  constructed  around  the  commutator  of  which  the  cur- 
rent generated  would  not  short-circuit.  In  other  words, 
the  current  could  not  be  produced  exterior  to  the 
machine. 
With  the  multiple  system  (Fig.  68)  the  conditions  are 


Fig.  68.  Multiple  Circuit. 

in  some  respects  reversed.  The  danger  of  a  short-cir- 
cuit occurring  in  any  branch  is  avoidable,  and  the  elec- 
tro-motive force  of  current  being  low,  there  would  appear 
to  be  no  difficulty  in  insulating  the  main  conductors. 
The  questions  arising  in  the  operation  of  this  system  re- 
late particularly  to  the  generator. 

Assuming  that  the  generator  is  so  constructed  as  to 
give  a  useful  effect  in  the  external  circuit  of  any  percent- 
age of  the  total  current,  say  75  per  cent.,  and  that  the 
resistance  of  the  lamp  used  is  200  ohms  instead  of  one 
ohm  (for  comparison  with  a  low-resistance  lamp  would 
obviously  be  unfair  to  a  system  in  which  lamps'  of  high 
resistance  only  are  employed),  the  internal  resistance 
of  the  generator  would  be  66.66  ohms,  and  the  total  re- 
sistance of  the  circuit  266.66  ohms.  .Suppose  now  that 
we  add  another  lamp  to  the  circuit  of  the  machine  ;  we 
reduce  the  external  resistance  to  100  ohms,  because  the 


122  ELECTRIC  LIGHTING  BY  INCANDESCENCE. 

current  has  now  two  paths  to  traverse,  each  of  200  ohms 
resistance.  The  total  resistance  of  the  external  circuit 

becomes  166.66  ohms,  and  — '—-  of  the  current  is  wast- 

luo.  ub 

ed  in  the  machine.  Let  the  number  of  lamps  be  ten ; 
then  we  have  an  external  resistance  of  20  ohms,  and  a 
total  resistance  of  86.66  ohms.  We  thus  obtain  in  the 

external  circuit  only  -^-^  of  the  current  generated,  or 
85.  bo 

about  23  per  cent.  Extending  the  calculation  to  one 
hundred  lamps,  thus  making  the  external  resistance  two 
ohms,  we  are  able  to  utilize  less  than  3  per  cent,  of  the 
current  generated.  In  order  to  be  able  to  operate  one 
hundred  lamps  with  a  utilization  of  50  per  cent,  of  the 
whole  current,  we  must,  therefore,  reduce  the  internal 
resistance  of  the  generator  to  two  ohms  ;  with  one  thou- 
sand lamps,  its  resistance  must  be  reduced  to  two-tenths 
of  one  ohm  ;  and  with  ten  thousand  lamps,  to  two  one- 
hundredths  of  an  ohm.  In  order  that  there  may  be  but 
little  loss  in  the  main  conductors  leading  from  the  gen- 
erator, they  must  be  of  large  size,  for  the  resistance  of  a 
copper  conductor  weighing  four  pounds  per  foot  is  sub- 
stantially four  one-hundredths  of  an  ohm  per  mile  ;  and 
as  there  are  two  mains,  the  total  resistance  of  the  con- 
ductors, costing,  as  bare  copper  at  30  cents  per  pound, 
$12,672,  is  eight  one-hundredths  of  an  ohm.  With  such 
a  conductor,  the  total  resistance  of  the  circuit  of  1,000 
lamps  would  be  .48  of  an  ohm,  divided  as  follows  :  gen- 
erator, ,2  ;  mains,  .08  ;  lamps,  .2.  There  would  thus  be 
wasted  in  the  generator  41f  per  cent,  of  the  current,  and 
in  the  mains  16f  per  cent.  ;  utilized  as  light,  41  f  per 


DIVISION  OF  CURRENT  AND  LIGHT.  123. 

cent.  To  bring  the  utilization  up  to  between  49  and  50 
per  cent.,  the  mains  must  weigh  32  pounds  per  foot,  and 
will  therefore  cost  $101,376.  The  respective  resistances 
will  then  be :  generator,  .2 ;  mains,  .01 ;  lamps,  .2  of  an 
ohm. 

In  corresponding  ratio  the  size  of  one  mile  mains  for 
10,000  lamps  must  be  increased,  if  we  desire  to  approach 
a  realization  in  light  of  even  50  per  cent,  of  the  current 
generated,  and  the  internal  resistance  of  the  generator 
must  be  reduced  to  two  one-hundredths  of  an  ohm.  We 
shall  not  pause  to  consider  the  character  of  a  generator 
of  the  required  power  and  of  so  low  an  internal  resist- 
ance, for  we  have  no  practical  data  upon  which  to  base 
an  opinion.  The  production  of  a  generator  of  the  resist- 
ance given,  combined  with  the  capacity  indicated,  is  at 
all  events  possible.  Concerning  the  requirements  of  any 
multiple-circuit  generator,  however,  we  are  enabled  to 
see  that  it  must  be  one  of  multiple  induction,  the  coils  of 
which  shall  be  automatically  joined  together  to  form  a 
multiple  internal  circuit,  which  shall  both  increase  the 
quantity  of  the  current  generated  and  reduce  the  inter- 
nal resistance  of  the  generator  in  proportion  as  the  num- 
ber of  lamps  in  the  external  circuit  is  increased  and  the 
external  resistance  reduced.  In  the  mechanical  construc- 
tion of  such  a  generator  there  is  a  wide  field  for  study 
and  experiment. 

Referring  now  to  the  multiple-series  system  (Fig.  69), 
it  is  evident  that,  in  operating  1,000  lamps  of  200  ohms 
resistance  each,  there  may  be  one  hundred  branches 
across  from  main  to  main,  and  in  each  branch  ten  lamps, 
which  would  make  the  external  resistance  of  the  circuit, 


124  ELECTRIC  LIGHTING  BY  INCANDESCENCE. 

not  including  that  of  the  mains,  20  ohms  (1Qx^QQ  =  20\ 

\     100  / 

With  a  resistance  in  the  mains  of  one  ohm,  and  in  the 
generator  of  five  ohms,  making  the  total  resistance  twen- 
ty-six ohms,  there  is  utilizable  as  light  the  ten- thirteenth 
part  of  the  current  generated,  or  about  77  per  cent.  Ap- 
plied to  lamps  of  low  resistance,  as  one  ohm  each,  the 


-f 


© 


Fig.  69.  Multiple-Series  Circuit. 

arrangement  would  have  to  be  materially  changed  ;  for, 
unless  changed,  the  external  resistance  of  the  lamp  cir- 
cuit would  be  but  one-tenth  of  an  ohm  (  =  .1  \ 

and  the  total  resistance  of  the  system  6.1  ohms  ;  whence 
it  follows  that  we  would  only  be  able  to  utilize  in  the 
production  of  light  1.64  percent.  o:f the  current  gene- 
rated. 

Reversing  this  arrangement  and  providing  10  branches, 
each  containing  100  lamps,  we  have  a  circuit  resistance  of 

10  ohms  (-      x     —  10  j;  and  with  a  generator  resistance 

of  2.5  ohms,  and  a  resistance  in  the  mains  of  .25  ohm, 
making  the  total  resistance  12.75  ohms,  we  are  enabled 
to  utilize  as  light  78  per  cent,  of  the  current  generated ; 
but  we  must  light  substantially  the  entire  hundred  lamps 


DIVISION  OF  CURRENT  AND  LIGHT. 


125 


in  each  branch  at  once  and  extinguish  them  all  at  once, 
or  else  we  must  waste  the  current  which  would  go  to  the 
lamps  in  equivalent  artificial  re- 
sistances when  we  extinguish  a 
part  of  the  lamps  ;  for,  as  the  cur- 
rent is  to  be  equally  divided  among 
all  the  branches,  a  branch  must  in 
practice  either  be  entirely  cut  off 
from,  or  its  entire  resistance  inter- 
posed in,  the  circuit. 

In  the  fourth  or  series-multiple 
system  of  subdivision  (Fig.  70),  as 
in  the  multiple- series  system,  the 
resistance  of  the  external  circuit 
may  be  anything  desired,  and 
there  may  be  operated  in  the  same 
circuit  very  many  different  combi- 
nations of  lamps.  The  main  con- 
ductor, which  is  single  as  in  the 
series  system,  is  cut  at  the  points 
at  which  light  is  desired,  and  from 
the  two  disconnected  ends  a  num- 
ber of  small  conductors  are  run 
each  to  a  lamp  or  a  series  of 
lamps.  In  the  operation  of  1,000 
lamps  by  this  system  there  may 
be,  say,  one  hundred  points  of 
divergence,  and  at  each  of  these 
points  ten  lines  of  wire  contain- 
ing one  lamp  each.  Thus  the  re- 
sistance of  the  lamp  circuit  is 


126  ELECTRIC  LIGHTING  BY  INCANDESCENCE. 

/1 00  V  1  \ 

made  10  ohms  t  --^-  -  =  10  J,  and  with  a  generator- 
resistance  of  2.5  ohms,  and  a  resistance  in  the  connecting 
conductors  of  .25  ohm,  we  utilize  as  light  78  per  cent,  of 
the  whole  current.  With  10,000  lamps  there  may  be  500 
points  of  divergence,  each  containing  20  lamps,  by  which 
arrangement  the  resistance  of  the  lamp  circuit  becomes 

25  ohms  (—  ^—  —  25  J  ;  and  with  a  generator  resist- 
ance of  5  ohms,  and  a  resistance  in  the  connecting  con- 
ductors of  1  ohm,  the  proportion  of  current  available  for 
light  is  80  per  cent,  of  the  total  production. 

We  might  continue  these  calculations  indefinitely,  but 
to  no  further  purpose.  The  flexibility  of  the  system  is 
obviously  such  as  to  permit  of  any  regular  combination 
of  lamps  whatever,  and  thus  to  obtain  any  external  re- 
sistance whatever  ;  and  it  will  be  found  to  permit  equally 
well  of  all  irregular  combinations,  so  that  in  one  division, 
where  the  volume  of  light  required  is  great,  there  may  be, 
say,  five  lamps  in  multiple,  and  in  the  next  division,  where 
the  volume  of  light  required  is  ordinary,  there  may  be 
ten  lamps  in  multiple,  each  of  the  latter  receiving  but 
one-fourth  as  much  current  as  each  of  the  former,  be- 
cause the  joint  resistance  of  the  ten  lamps  is  .1  ohm, 
while  the  joint  resistance  of  the  five  lamps  is  .2  ohm; 
and  the  ten  lamps  receive  but  half  as  much  current  as 
the  five  lamps,  while  the  number  of  lamps  is  doubled. 
The  closing-up,  short-circuiting,  or  reducing  the  resist- 
ance of  any  division  acts  simply  to  reduce  the  resistance 
of  the  whole  circuit,  in  the  same  manner  as  removing  a 
portion  of  the  lamps  in  a  simple- series  system.  The  re- 


DIVISION  OF  CURRENT  AND  LIGHT.  137 

lative  advantages  of  the  multiple-series  and  the  series- 
multiple  systems  can  only  be  determined  by  the  number 
of  lamps  operated  from  a  single  source  and  the  practical 
operation  of  both  systems,  although  there  are  considera- 
tions of  simplicity  which  would  seem  to  favor  the  series- 
multiple  arrangement  of  lamps,  whose  connection  with  a 
Iinc3  of  dwellings  is  illustrated  in  Fig.  71. 


128 


ELECTRIC  LIGHTING  BY  INCANDESCENCE, 


3 


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CHAPTER  X. 

KEGTTLATOKS  AND   SWITCHES. 

4  LTHOUGH  it  is  matter  of  common  knowledge  that  a 
carbon  loop  or  pencil,  intensely  heated  by  the  pas- 
sage of  the  electric  current,  becomes  luminous,  it  is  not 
generally  known  what  proportion  the  degree  of  lumi- 
nosity bears  to  the  strength  of  current.  The  precise  re- 
lations of  the  current  supplied  and  the  light  produced 
have  never  been  determined ;  but  results  which,  it  is  be* 
lieved,  closely  approximate  the  truth  were  first  obtained 
in  August,  1878. 

A  Sawyer-Man  lamp  of  high  resistance  (.6  of  an  ohm) 
was  employed  in  the  tests  then  made  ;  but  it  should  be 
borne  in  mind  that,  without  reference  to  the  length  or 
cross-section  of  the  carbon,  so  long  as  the  current  sup- 
plied is  in  proportion  to  its  length  and  cross-section,  the 
percentages  observed  in  one  lamp  are  the  percentages  of 
all  lamps  in  which  wastage  of  the  carbon  by  chemical  ac- 
tion is  obviated.  Disintegration  at  the  points  of  contact 
when  these  are  imperfect,  mechanical  disengagement  of 
particles  of  the  carbon,  and  rupture  due  to  imperfections 
in  the  constitution  of  the  carbon  are  occurrences  common 
.to  al]  incandescent  lamps. 

A  dynamo-electric  machine  wound  expressly  for  the 
purpose,  and  driven  at  an  unvarying  speed,  was  used  ; 

129 


130 


ELECTRIC  LIGHTING  BY  INCANDESCENCE. 


and  as  there  was  abundance  of  power,  and  as  the  speed 
remained  constant  under  almost  any  circumstances,  it 
was  deemed  necessary,  in  order  to  obtain  a  satisfactory 
result,  that  the  resistance  external  to  the  machine  should 
be  kept  constant,  Therefore  the  internal  resistance  of 
the  lamp  to  be  experimented  upon  was  measured,  and  it 
was  found  to  be  as  stated.  A  new  form  of  current-regu- 
lator, afterwards  known  as  the  Sawyer-Man  switch  (Fig. 
72),  was  employed  in  the  tests.  The  poles  of  the  gene- 

.60 


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Fig.  72.  The  Sawyer-Man  Switch. 

rator  had  connections  at  the  +  and  —  points,  A  being 
a  sliding-bar,  and  the  cross-piece  B  being  a  spring  con- 
tact-piece brought  to  a  bearing  upon  the  two  rows  of 
studs  1,  2,  3,  4,  5,  6,  7,  8,  accordingly  as  it  is  moved 
backward  or  forward.  Whatever  position  the  cross- 
piece  assumes,  it  will  be  noted  that  the  resistance  of  the 
circuit  from  the  +  to  the  —  point  is  the  same.  In  the 
position  shown,  all  the  current  traverses  the  lamp.  With 
the  contact-piece  B  bearing  upon  the  studs  7,  7,  two 


REGULATORS  AND  SWITCHES. 

paths  for  the  current  are  afforded,  one  by  way  of  a  re- 
sistance of  .10  ohm  and  the  lamp  outward,  making  a 
total  resistance  of  .70  ohm  in  that  circuit,  and  the  other 
by  way  of  resistances  of  2.10,  .70,  .35,  .21,  .14,  .10,  and 
.60  ohms  outward,  the  sum  total  of  which  series  of  resist- 
ances is  4.2  ohms,  thus  sending  through  the  lamp  six- 
sevenths  of  the  current,  while  maintaining  the  resistance 
from  the  -)-  to  the  —  point  the  same. 

It  was  found  that  when  the  volume  of  current  supplied 
to  the  lamp  was  three-sevenths  of  the  whole  current,  the 
contact-piece  B  bearing  upon  the  studs  4,  4,  the  carbon 
was  brought  to  a  low  red-heat.  With  four-sevenths  of 
the  current  supplied  to  the  lamp,  the  carbon  gave  a 
light  of  about  one  candle  ;  with  five-sevenths  of  the  cur- 
rent, the  light,  measured  by  a  Sugg  photometer,  was 
three  candles  ;  with  six-sevenths  of  the  current,  nine 
candles  ;  with  the  whole  current,  twenty-seven  candles. 
When  the  contact  piece  B  was  bearing  upon  the  studs 
1,  1,  the  whole  current  passed  through  the  artificial  re- 
sistance of  .60  ohm.  The  gradations  of  light  by  this 
means  being  too  sudden  (from  less  than  one  candle-light 
to  three  candle-light,  from  three  to  nine,  and  from  nine 
to  twenty-seven  candle-light),  the  resistances  were  subse- 
quently changed  so  as  to  admit  to  the  lamp  first  one-half 
of  the  current,  then  five-eighths,  three-quarters,  seven- 
eighths,  fifteen-sixteenths,  thirty -one-thirty-seconds,  and 
finally  the  whole  current.  With  this  arrangement  the 
gradations  were  gradual  and  pleasing. 

The  disparity  between  the  volume  of  current  supplied 
and  the  intensity  of  the  light  obtained  is  very  clearly  in- 
dicative of  the  requirements  of  an  incandescent  lamp. 


132  ELECTRIC  LIGHTING  BY  INCANDESCENCE. 

Since  five-sevenths  of  the  total  current  for  a  single  lamp 
produces  but  three  candle-light,  while  the  whole  current 
produces  twenty-seven  candle-light,  or  nine  times  as 
much,  it  follows  that  in  order  to  secure  the  maximum 
economy  the  carbon  must  be  raised  to  a  high  tempera- 
ture. For  if  we  have  a  supply  of  current  equal  only  to 
the  maximum  requirements  of  fifty  lamps,  from  which 
we  may  obtain  a  sum  total  of  1,350  candles,  we  cannot 
divide  this  current  among  seventy  lamps  without  sus- 
taining enormous  loss,  as  the  sum  total  of  light  given 
Iby  the  seventy  lamps  will  be  but  210  candles,  while 
the  expenditure  of  power  will  be  the  same.  There 
is  a  compensating  influence  in  the  case  of  lamps  in 
series  driven  by  a  dynamo-generator,  consisting  in  the 
increased  percentage  of  current  exterior  to  the  gen- 
erator when  the  resistance  of  the  external  circuit  is  in- 
creased. 

To  sustain  the  high  temperatures  necessary  to  the 
economical  operation  of  an  incandescent-lighting  system 
the  carbon  must  be  hard,  dense,  and  substantial ;  and  in 
the  absence  of  these  qualities  is  found  the  explanation 
for  the  inefficiency  of  fine,  filamentary  carbons,  which 
can  never  be  safely  brought  above  the  temperature  of  a 
gas-flame.  Carbon  incandescence  (that  of  white  light), 
unlike  the  incandescence  of  an  iron  or  platinum  conduc- 
tor, is  of  two  grades  and  various  intensities.  In  the  first 
the  carbon  is  intensely  white,  and  its  form  optically 
broadened  and  lost  in  a  surrounding  haze  of  light.  In 
the  second  and  more  intense  incandescence  its  form 
stands  out  sharply  defined,  and  it  appears  no  longer 
opaque  but  limpid,  seemingly  translucent,  like  the  body 


REGULATORS  AND  SWITCHES. 


133 


of  the  sun.     It  is  to  this  degree  of  intensity  that  econo- 
mical lighting  by  incandescence  is  confined. 

The  Sawyer-Man  switch  affords  a  ready  means  of  divid- 
ing the  current  in  any  desired  manner,  while  maintain- 
ing the  resistance  of  a  circuit  constant.  Thus  any  num- 
ber of  lamps  provided  with  it  may  be  operated  by  a 
single  generator,  and  any  portion  of  them  may  be  regu- 
lated to  any  desired  degree  of  intensity  without  affecting 
other  lamps  in  circuit.  The  objection  to  its  use  consists 


Fig  73.  Small  Sawyer 
Switch.  . 


Pig.  74.  Switch  apart. 

in  the  fact  that  when  a  lamp  is  extinguished  the  work  of 
the  generator  is  not  lessened,  but  the  entire  current  that 
served  to  operate  the  lamp  is  wasted  in  heating  an  artifi- 
cial resistance.  It  was  this  consideration  that  led  to  the 
designing  of  the  graduating  switch  (Fig.  73),  which  is 
fixed  to  the  wall  of  a  room  or  in  any  other  convenient 
place,  or  attached  to  the  lamp-fixture.  In  this  switch, 
which  is  illustrated  apart  in  Fig.  74,  there  is  an  insulat- 
ing disk,  upon  which  are  fixed  four  brass  segments  of  a 
€ircle.  Over  this  disk  is  placed  the  brass  enclosing- cap, 
through  which  passes  loosely  a  slotted  iron  pin  carrying 


134 


ELECTRIC  LIGHTING  BY  INCANDESCENCE. 


a  brass  contact-bar,  which  is  forced  to  a  bearing  upon 
the  brass  segments  by  means  of  a  steel  spring  coiled  in 
the  head  of  the  cap.  Upon  the  end  of  the  iron  pin  the 
finger-piece  is  finally  screwed.  By  turning  the  finger- 
piece  in  one  direction  or  the  other  the  light  is  turned  on 
or  off,  or  regulated  to  intermediate  points  of  intensity. 
In  Fig.  75  the  switch,  as  attached  to  the  arm  of  a  chan- 


Fig.  75.  Switch  attached  to  Bracket. 


deller  or  bracket,  is  illustrated,  the  circular  case  at  the 
end  of  the  arm  being  shown  partly  in  section.  The 
lamp  is  fixed  to  the  nipple  above  the  switch-case,  and  the 
insulated  conducting- wires  pass  through  the  hollow  arm. 
The  connections  of  the  switch  are  shown  in  Fig.  76. 
When  both  ends  of  the  cross-bar  A  are  bearing  upon 


REGULATORS  AND  SWITCHES. 


135 


segment  4,  the  whole  current  passes  through  the 
lamp.  When  the  cross-bar  bears  upon  segments  3  and 
4,  the  current  divides,  a  part  passing  through  the  lamp 
and  part  through  the  artificial  resistance  of  .50  and  .25 
ohm.  When  the  cross-bar  bears  u|>on  segments  2  and  4, 
the  current  is  divided  between  the  lamp  and  the  artifi- 
cial resistance  of  .25  ohm.  Bearing  upon  segments  1 
and  4,  the  lamp  is  short-circuited  and  practically  re- 
ceives no  current.  The  artificial  resistances  are  prefera- 


Fig.  76.  Switch-Connections. 

bly  made  of  naked  copper  wire  exposed  to  the  air  or 
embedded  in  plaster-of-Paris  and  enclosed  in  the  case 
(Fig.  75). 

By  means  of  this  switch  it  is  clear  that  when  a  lamp 
is  extinguished  its  resistance  is  removed  from  the  circuit, 
and  the  current  is  not  wasted  in  heating  an  artificial  re- 
sistance. But  in  order  that  the  changes  which  take 
place  in  its  circuit  may  not  add  to  or  lessen  the  volume 
of  current  supplied  to  other  lamps,  it  is  necessary  that 
the  changes  which  occur  in  its  circuit  shall  in  some  man- 
ner react  upon  the  source  of  the  current ;  and  this  brings 


136  ELECTRIC  LIGHTING 'BY  INCANDESCENCE. 

us  to  the  consideration  of  regulators  operating  to  supply 
current  in  proportion  to  the  requirements  of  a  system. 

Before  taking  up  this  subject,  however,  a  form  of 
switch  designed  for  use  upon  a  circuit  of  lamps  in  series, 
where  interruption  of  the  circuit  at  any  one  lamp  would, 
without  it,  result  in  extinguishing  all  the  lamps  in  cir- 
cuit, will  be  described. 

In  Fisr.  77  the  switch  is  shown  as  fixed  to  the  wall  of 


Fig.  77.  Electro-Magnetic  Switch. 

the  room,  and  also  with  its  cover  and  finger- piece  apart. 
In  Fig.  78  the  interior  mechanism  is  illustrated.  In  Fig. 
79  we  have  a  diagram  of  the  connections. 

A  is  the  magnet-lever  ;  B  and  C  are  other  levers  ;  B  is 
a  cam  operating  to  raise  and  lower  lever  C,  which  is 
pressed  downward  by  coiled  spring  H.  Lever  B  is 
pressed  upward  by  insulated  spring  E.  F  and  Gr  are 
stop-pins,  and  I  is  an  artificial  resistance. 

In  the  position  shown  lever  A  is  in  contact  with  stop- 


REGULATORS  AXD  SWITCHES. 


137 


pin  G.  Lever  B  is  in  contact  with  stop-pin  F,  but  not 
with  lever  A.  Lever  C  is  in  contact  with  cam  D,  but 
not  with  lever  A.  The  current,  therefore,  passes  from 


Fig  78.  Mechanism  of  Switch. 

the  +  point  through  the  coils  of  the  magnet  to  the  lamp 
and  outward  at  the  -  -  point,  the  armature-lever  being 
attracted  to  its  contact  with  stop -pin  G  and  the  entire 


Xajnp 


Fig.  79.  Electro-Magnetic  Switch-Connections. 

current  passing  through  the  lamp.  To  extinguish  the 
light  cam  D  is  moved  a  little  to  the  right,  but  not  leav- 
ing its  contact  with  lever  C,  when  lever  C  is  pressed 


138 


ELECTRIC  LIGHTING  BY  INCANDESCENCE. 


downward  to  a  contact  with,  lever  A.  The  lamp  is  thus 
short-circuited,  the  current  passing  from  the  +  point 
through  levers  A  and  C  to  the  cam  D  and  outward  at 
the  -  -  point.  To  give  the  lamp  sufficient  current  to 
produce  one-half  its  full  light,  the  cam  D  is  moved  fur- 
ther to  the  right,  so  as  to  pass  from  its  contact  with 
lever  C.  Then  lever  C,  falling  further,  forces,  lever  A  to 
make  connection  with  lever  B,  and  the  current  divides,  a 
part  flowing  from  the  -f-  point  through  the  coils  of  the 
magnet  and  the  lamp  outward,  and  the  remainder  flow- 
ing, by  way  of  levers  A  and  B  and  resistance  I,  outward 
to  the  —  point.  With  the  cam  turned  to  the  interme- 
diate point  the  lamp  is  extinguished.  Turned  as  far  as 
it  will  go  to  the  right,  one-half  of  the  light  is  emitted. 
Turned  as  far  as  it  will  go  to  the  left,  the  maximum  in- 


Fig.  80.  Carbon  Resistance. 

tensity  of  light  is  produced.  In  the  event  of  an  inter- 
ruption of  the  lamp-circuit  the  lever  A,  which,  when  the 
circuit  is  complete,  is  attracted  by  the  magnet,  drops  to 
contact  with  lever  B,  and  the  circuit  is  re-established  by 
way  of  resistance  I.  Lever  A  can  only  be  drawn  towards 
the  magnet  when  the  pressure  of  spring  H  is  removed 
by  raising  lever  C  from  its  contact  with  lever  A. 

A  form  of  artificial  resistance  useful  in  electric  light- 
ing is  illustrated  in  Fig.  80,  in  which  a  rod  of  carbon  is 


REGULATORS  AND  SWITCHES.  139 

held  in  brass  connecting-clamps  upon  a  soapstone  base. 
A  thin  piece  of  platinum,  to  establish  perfect  contact,  is 
placed  between  the  end  of  the  carbon  and  a  plate  of 
brass  upon  which  the  upper  set-screw  presses.  Copper 
wire  for  artificial  resistances  is  preferable  to  iron  wire  of 
equal  diameter,  owing  to  the  greater  surface  exposed  to 
radiation  and  convection  of  heat  by  the  better  conduc- 
tor ;  and  copper  ribbon,  for  the  same  reason,  is  preferable 
to  either. 

In  the  Edison  and  Maxim  systems  of  lighting  the  ordi- 
nary make-and-break  circuit  switch  is  employed.  In  re- 
spect to  simplicity  it  cannot  be  improved,  but  it  affords 
no  means  of  graduating  the  light,  which  must  either  be 
kept  at  its  full  power  or  entirely  extinguished.  The 
Edison  switch,  however,  like  the  switches  employed  in 
the  Sawyer  system,  does  not  interpose  current- wasting 
resistances  when  no  light  is  required,  the  supply  of  elec- 
tricity being  supposed  to  be  regulated  at  the  generator  in 
proportion  to  the  requirements  of  the  circuit. 

Many  attempts  at  automatic  regulation  of  the  supply 
of  current  have  been  made  both  in  this  country  and 
abroad,  the  nearest  approach  to  its  realization  by  for- 
eign electricians  being  the  device  of  Dr.  Siemens,  who  in 
January,  1879,  proposed  to  place  a  number  of  carbon 
disks  in  an  insulating  tube,  pass  the  current  through 
them,  and  by  means  of  a  platinum  wire,  also  in  the  cir- 
cuit, to  vary  the  conductivity  of  the  carbon  pile  by  vary- 
ing the  pressure  of  the  disks  upon  each  other.  For 
several  reasons,  unnecessary  to  state,  this  arrangement 
could  have  no  practical  application  in  an  electric-light- 
ing system. 


140 


ELECTRIC  LIGHTING  BY  INCANDESCENCE. 


The  conditions  to  be  met  are  not  so  easily  met  as  might 
appear  from  a  superficial  examination.  Let  us  suppose 
that  there  are  ten  lamps,  of  one  ohm  resistance  each, 
arranged  in  multiple  circuit,  and  that  each  lamp  receives 
one-tenth  "part  of  the  whole  current.  Suppose,  now, 
that  we  add  a  lamp ;  then  each  lamp  receives  but  one- 
eleventh  of  the  former  current.  We  must,  therefore,  so 
increase  the  supply  that  each  of  the  eleven  lamps  shall 


Mg.  81.  The  Maxim  Regulator. 

receive  as  much  current  as  each  of  the  ten  lamps  received 
before.  To  accomplish  this  increase,  there  are  two  very 
similar  forms  of  regulators,  the  first  of  which  was  patent- 
ed by  Sawyer  &  Man,  June  25,  1878,  and  the  second  of 
which  was  recently  devised  by  Mr.  Maxim.  The  latter 
is  illustrated  in  Fig.  81.  Its  operation  is  as  follows  :  In 


REGULATORS  AND  SWITCHES. 

one  of  the  branches  across  the  two  main  conductors  of  a. 
multiple-circuit  system  is  placed  the  electro-magnet  A. 
A  proportion  of  the  current,  dependent  upon  the  diffe- 
rence in  the  resistance  of  the  magnet  branch  and  that  of 
all  the  multiple  lamp  branches,  traverses  tlie  magnet- 
coils  ;  and  as  this  proportion  varies  according  to  the  num- 
ber of  lamps  in  circuit,  it  is  obvious  that  the  force  with 
which  its  armature  is  attracted  varies.  When  the  sup- 
ply of  current  is  insufficient  the  armature  is  released,  and 
by  means  of  a  system  of  gear-wheels,  continuously  in  mo- 
tion, the  shaft  B  is  rotated  in  one  direction,  and  the  com- 
mutator-brushes of  the  generator  are  thereby  so  set  as  ta 
supply  a  greater  volume  of  current.  When,  on  the  other 
hand,  the  supply  of  current  becomes  too  great,  by  reason 
of  the  removal  of  lamps  from  the  circuit,  the  armature  is 
attracted,  and  through  the  system  of  gear-wheels  men- 
tioned the  shaft  B  is  rotated  in  the  opposite  direction, 
and  the  commutator-brushes  are  thereby  so  set  as  to 
yield  a  less  volume  of  current.  These  are  the  principles 
of  this  regulator,  which  it  is  only  reasonable  to  suppose 
is  as  yet  undeveloped.  The  considerable  changes  in  cur- 
rent-force necessary  to  its  operation  are  such  as  to  cause 
a  rhythmical  increase  and  decrease  of  the  intensity  of 
light  from  the  lamps  connected  with  it,  owing  to  the 
failure  of  the  armature  mechanism  to  act  until  the 
strength  of  the  current  has  too  far  exceeded  or  fallen 
too  far  below  the  point  at  which  it  must  remain  in  order 
to  produce  no  appreciable  alteration  in  the  intensity  of 
the  light.  The  interposition  of  a  sensitive  relay,  operat- 
ing to  open  and  close  the  circuit  of  the  magnet  A,  in- 
stead of  placing  the  magnet  A  in  the  main  circuit,  would 


142  ELECTRIC  LIGHTING  BY  INCANDESCENCE. 

have  operated  to  maintain  the  intensity  of  the  light 
constant.* 

In  the  Sawyer  system  of  regulating  the  supply  of  cur- 
rent, without  regard  to  the  speed  of  the  generator  or  the 
electro-motive  force  of  the  current  (Fig.  82),  we  have  first 


*  Fig.  82.  System  of  Regulation. 

to  find  the  proper  relation  between  the  strength  of  cur- 
rent and  the  number  of  lamps  to  be  operated.  Let  us 
suppose  that  there  are  ten  lamps  arranged  in  series, 
and  that  the  full  current  is  exactly  sufficient  to  operate 
these  lamps  at  their  maximum  intensity.  At  any  point 
in  the  circuit  we  place  an  electro-magnet,  B,  having  the 
sensitiveness  of  a  telegraphic  relay.  The  relation  of  this 

*  In  Letters-Patent  of  the  United  States,  No.  223,659,  of  January  20, 
1880,  granted  to  Professors  Thomson  and  Houston,  members  of  the  Frank- 
lin Institute  of  Philadelphia,  the  principles  of  this  regulator  are  described, 
with  the  following  claim  : 

"  As  a  motor  for  effecting  the  adjustment  of  the  commutator  collecting 
brushes,  an  electro-magnet,  M,  traversed  by  the  current,  or  a  portion  of  the 
current,  of  the  machine,  whose  attraction  upon  its  armature,  N,  moves  said 
commutator  collecting  brushes  in  one  direction,  motion  in  the  other  direc- 
tion being  obtained  by  the  action  of  a  spring." 


REGULATORS  AND  SWITCHES.  143 

magnet  towards  the  regulating  apparatus  is  actually  the 
same  as  the  relation  of  the  telegraphic  relay  towards  the 
local  telegraphic  instrument.  The  armature-lever  of  this 
magnet  is  set  between  two  contact-points,  between  which 
it  plays  without  appreciable  motion.  Indeed,  both 
points  may  be  in  actual  contact  with  the  lever,  so  that 
the  latter  shall  not  move  at  all ;  but  the  local  circuit 
shall  be  changed  by  the  change  in  resistance  due  to  the 
mere  difference  in  pressure  of  the  relay -lever  upon  the 
separate  contact-points.  Thus  arranged,  variations  in 
the  strength  of  the  lighting  current,  sensible  only  to  a 
galvanometer,  may  be  made  to  operate  the  circuit  of  a 
local  battery,  and  thus  to  energize  electro-magnetic  regu- 
lating mechanism. 

Let  C  C  be  tho  ten  lamps  in  circuit,  and  A  a  rotating* 
contact-lever.  D  D  represent  a  series  of  ten  artificial 
resistances,  the  sum-total  of  which  is  2.5  ohms.  The  sum- 
total  of  the  resistance  of  the  ten  lamps  in  circuit  is  also- 
2.5  ohms.  When  all  the  lamps  are  in  operation,  the  cir- 
cuit passes  from  the  -f-  point  to  the  stud  No.  1,  and 
thence  through  relay  B  and  the  ten  lamps  C  C  to  the 
—  point.  The  resistance  of  B  is  for  convenience  disre- 
garded, as  it  is  but  a  fraction  of  the  total  resistance. 
Suppose,  now,  that  we  extinguish  half  of  the  lamps  by 
short-circuiting  them.  The  resistance  of  the  lamp  cir- 
cuit is  reduced  to  1.25  ohms,  and  the  effect  of  the  current 
upon  B  is  correspondingly  increased.  Its  lever  at  once 
actuates  the  regulating  mechanism,  which  moves  lever  A 
to  contact  with  stud  6,  thus  bringing  the  resistance  of 
the  circuit  to  its  normal  point — viz.,  2.5  ohms.  The  same 
action  ensues  whenever  a  lamp  is  short-circuited,  and 


144 


ELECTRIC  LIGHTING  BY  INCANDESCENCE. 


the  reverse  action  whenever  an  additional  lamp  is  thrown 
into  the  circuit.  In  practice  the  resistances  D  D  are 
greater  in  number  and  each  of  a  less  value  than  described, 


Fig.  83.  The  Sawyer  Electro-Magnetic  Regulator. 

but  the  sum-total  of  all  remains  the  same.  The  lever  of 
B  in  practice  is  in  constant  vibration  between  its  contact- 
points,  and  the  lever  A  is  in  constant  vibration  between 


REGULATORS  AND  SWITCHES.  145 

two  contiguous  studs  or  segments  of  the  circle,  in  addi- 
tion to  its  positive  movements  over  a  greater  or  less 
number  of  studs. 

In  the  engraving  (Fig.  83),  from  a  photograph,  is  illus- 
trated the  Sawyer  electro-magnetic  regulator.  The  large 
gear-wheel,  whose  shaft  carries  a  rotating  contact-arm, 
corresponding  to  lever  A  of  Fig.  82,  making  connection 
seriatim  with  a  number  of  insulated  segments  of  a  circle 
enclosed  in  an  oval-top  case,  is  set  in  motion  by  a  pinion 
on  the  shaft  of  a  small  reversing  electric  engine  enclosed 
in  the  central  round  metal  case.  When  there  is  too 
great  a  supply  of  current,  the  armature-lever  of  the  mag- 
net in  the  main  circuit  establishes  the  local  circuit  of  a 
commutator  which  drives  the  engine  in  one  direction ; 
when  there  is  too  little  current,  the  armature-lever  estab- 
lishes the  circuit  of  a  second  commutator  which  drives 
the  engine  in  the  opposite  direction.  In  the  first  instance 
resistance  is  introduced  in  the  main  circuit.  In  the  sec- 
ond instance  resistance  is  removed  from  the  circuit. 

Imperfections  due  to  the  oxidization  of  contact-points 
in  the  electric  engine,  and  the  occasional  failure  of  the 
engine  to  respond  to  changes  in  its  circuit,  led  to  the 
abandonment  of  what  was  otherwise  a  successful  regula- 
tor, and  the  substitution  therefor  of  hydraulic-cylinder- 
and-piston  mechanism,  constituting  the  regulator  shown 
in  Fig.  84,  which  is  also  from  a  photograph. 

The  internal  arrangements  of  the  regulator  are  shown 
in  Fig.  85,  in  which  J  is  a  hollow  metal  base  containing 
the  various  resistances'  connected  with  the  18  pieces,  F, 
corresponding  to  the  10  studs  or  segments  of  Fig.  82.  B 
is  a  cylinder  fixed  to  the  base  J  and  open  at  the  top. 


Fig.  84   Hydraulic  Regulator. 


Fig.  80.  Hydraulic  Eegtilator  Mechanism. 


148  ELECTRIC  LIGHTING  BY  INCANDESCENCE. 

Closely  fitting  in  cylinder  B  is  the  cylinder  A,  open  at 
the  bottom.  Supported  by  a  tube  passing  through  the 
base,  and  closely  fitted  in  cylinder  A,  is  the  piston  C. 
Insulated  upon  one  side  of  cylinder  B  is  a  stationary  con- 
tact-plate, E,  to  which  one  pole  of  the  generator  is  at 
tached.  Insulated  upon  the  opposite  side  of  the  cylinder 
are  the  18  grooved  central  plates  F.  Running  in  the 
grooves  of  E  and  F  are  two  contact-arms,  G  and  H, 
whose  pressure  upon  E  and  F  is  regulated  by  spring  I. 
The  current,  therefore,  passes  by  way  of  plate  E  to  arms 
H  and  G  and  a  contact-plate  F  outwardly,  as  shown  in 
the  regulator-connections,  Fig.  82.  The  ends  of  the  cores 
of  an  electro-magnet,  K,  provided  with  an  armature-lever, 
L,  pass  through  the  piston-head,  and  serve  to  open  and 
close  the  valves  N  M.  When  the  magnet  K  is  not  ener- 
gized, a  coiled  spring  forces  the  armature  away,  and  valve 
IN"  is  opened  to  the  flow  of  a  stream  of  water,  and  valve  M 
is  closed  against  its  escape  into  the  lower  chamber  and 
outwardly  through  the  exit-tube  O.  Therefore  the  cylin- 
der A  rises.  When  the  magnet  is  energized,  the  valve  N 
is  closed  and  the  ingress  of  water  stopped,  while  valve  M 
is  opened  and  the  water  contained  in  the  upper  chamber 
is  allowed  to  escape.  The  cylinder  A  then  falls  by  its 
own  weight  as  rapidly  as  the  escaping  water  permits. 
By  a  suitable  arrangement  the  waste  water  is  used  to 
cool  the  various  artificial  resistances.  The  local  circuit 
of  the  magnet  K  is  established  by  the  back  contact  of  the 
relay -lever.  The  movements  of  the  cylinder  A  are 
smooth  and  the  changes  rapid.  The  contacts  of  G  and 
H  with  F  and  E  are  of  a  firm  and  substantial  character. 
With  a  pressure  of  10  pounds  of  water  and  a  piston 


REGULATORS  AND  SWITCHES.  149 

area  of  10  square  inches,  the  cylinder  A  is  raised  above 
its  weight  with  a  force  of  50  pounds  ;  and  as  its  weight 
is  50  pounds,  it  obviously  falls  with  the  same  force. 
With  a  piston  area  of  80  square  inches  and  20  pounds 
pressure  of  water,  a  circuit  is  operated,  with  singularly 
rapid  changes  in  the  direction  of  movement  of  the  cy- 
linder, with  an  upward  force  in  the  cylinder  of  1,600 
pounds.  There  is  apparently  no  limit  to  the  powerful 
effects  thus  producible  by  minute  changes  in  the  strength 
of  current  supplied  to  a  system  of  lamps.  By  means  of 
these  regulators,  the  changes  in  the  circuit  occasioned  by 
the  Sawyer  switches  for  graduating  the  light  are  in- 
stantly balanced ;  but  the  fact  remains  that  as  much 
power  is  expended  in  driving  the  generator  when  there 
are  a  few  as  when  there  are  many  lamps  in  circuit,  and 
in  a  general  distributing  system,  where  economy  is  the 
prime  consideration,  such  regulators,  however  perfect  in 
their  operation,  can  have  no  practical  application. 


CHAPTER  XL 

GENERAL   DISTRIBUTION. 

, 

fTHE  date  of  the  original  conception  of  the  idea  of  a 
general  distribution  system,  supplying  electricity 
Irom  a  central  station  to  an  entire  city,  and  the  identity 
of  the  person  first  conceiving  this  idea,  will  probably 
never  be  satisfactorily  determined.  The  one  most  de- 
serving of  honor  in  this  respect  would  appear  to  be 
Starr.  As  conceived  by  Sawyer,  thirty  years  later  than 
the  time  of  Starr,  it  was  patented  in  the  United  States 
August  14,  1877,  and  it  is  believed  that  this  was  the  first 
systematic  reduction  of  the  idea.  The  illustration  (Fig. 
86)  is  a  fac-simile  of  the  first  sheet  of  drawings  accom- 
panying the  specification,  printed  by  the  United  States 
Patent  Office  :  R  being  the  central  station,  in  which  the 
generators  &,  a\  a\  a3  are  located ;  &,  blocks  of  houses  ; 
c,  points  of  divergence  of  mains  to  lamps,  e  ;  and  d,  back 
areas.* 

*  The  following  statement  occurs  in  the  specification  of  these  Letters- 
Patent  : 

"  The  object  of  my  invention  is  to  supply  the  streets,  blocks,  or  buildings 
of  a  town  or  city  in  a  practicable  manner  with  any  desired  quantity  of  elec- 
tricity for  the  purposes  of  electric  illumination,  electro-plating,  the  running 
of  electro-magnetic  engines,  etc.  I  place  the  generator  or  generators  of 
electricity  in  any  convenient  portion  of  a  locality,  whence  I  carry  the  neces- 
sary conductors  over  or  under  ground  to  the  streets,  blocks,  or  buildings  in 
which  the  current  is  to  be  utilized.  In  place  of  electric  conductors  leading 
from  a  central  station,  I  may  substitute  tubes  or  pipes,  through  which  water 

150 


GENERAL  DISTRIBUTION. 

The  considerations  involved  in  a  general  distributing 
system  are  of  a  more  complex  character  than  has  yet 
been  indicated.  In  a  system  in  which  the  lamps  are 
arranged  in  series  the  introduction  in  circuit  of  addi- 
tional lamps  must  operate  to  increase  the  electro -motive 
force  of  the  current  supplied  to  the  circuit.  On  the 
other  hand,  in  a  system  in  which  there  is  a  multiple 
arrangement  of  lamps  the  introduction  in  circuit  of  ad- 
ditional lamps  must  operate  to  increase  the  quantity  of 
current  supplied  to  the  circuit.  In  a  combination  of 
these  two  systems  there  must  be  a  combination  of  the 
two  operations. 

It  may  be  assumed  at  the  outset  that  in  any  practical 
distributing  system,  the  power  expended  at  the  generat- 
ing station  in  producing  current  must  be  proportionate 
to  the  current  requirements  of  the  system,  for  obviously 
we  cannot  economically  expend  as  much  power  in  ope- 
rating a  few  lamps  as  in  operating  a  large  number  of 
lamps.  When  we  reduce  the  number  of  lamps  it  is 
necessary  that  we  correspondingly  reduce  the  expendi- 
ture of  power  in  current  production  as  well  as  the  sup- 
ply of  current  to  the  circuit  of  the  lamps.  To  a  certain 
extent  this  must  be  done  automatically  ;  and  since  power 
is  already  provided  with  the  practical  adjuncts  of  con- 

or  compressed  air  is  carried  to  a  building,  there  to  drive  magneto-electric 
apparatus,  etc.,  for  local  work.  The  advantages  of  my  invention  are  that  it 
enables  householders  to  obtain  a  supply  of  electricity  for  any  purpose  with- 
out the  care  and  inconvenience  attending  the  maintenance  of  local  batte- 
ries; that  it  greatly  reduces  the  cost  of  electricity  to  consumers;  and  that  it 
renders  practicable  the  lighting  of  buildings  by  electricity.  I  do  not  limit 
myself  in  any  way  as  to  the  number  of  conduits  for  any  locality,  or  the 
purpose  for  which  the  electricity  is  used  in  combination  with  my  central 
station." 


152 


ELECTRIC  LIGHTING  BY  INCANDESCENCE. 


trol,  we  must  look  to  the  electric  regulator  for  the  inter- 
mediary means  of  supplying  current  in  proportion  to  the 
demand. 


Jive&ve. 


S4 


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j  [ 

I 

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i 

L 

j 

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L 

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l 

1 

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— 

i 

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-i 

— 

; 

— 

i 

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^\ 

i 

•q— 

i 

| 

' 

— 

i 

— 

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i*r 

1! 

j 

J 

j 

il  i 

M  1 

J  ^^ 

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_ii— 

Fig.  86.  General  Distribution. 

To  a  limited  extent,  starting  from  a  point  of  minimum 


GENERAL  DISTRIBUTION.  153 

efficiency,  we  may  economically  increase  the  value  of  the 
current  by  increasing  the  speed  of  the  generator.  In 
this  we  have  the  first  element  of  variability  in  genera- 
tion. Beyond  this  point,  we  may  increase  the  value  of 
the  current  by  increasing  the  intensity  of  the  magnetic 
field,  in  which  consists  the  second  element  of  variability  ; 
and  as  a  third  element  of  variability  we  have  the  con- 
necting in  circuit  of  additional  generators  or  parts  of 
generators.  In  Fig.  87  the  apparatus  of  a  distributing 
system,  comprising  all  three  elements,  is  represented. 

The  generating  elements  C  D  E  F  are  constantly  in 
motion,  and  practically  they  consume  power  in  propor- 
tion to  the  intensity  of  their  magnetic  fields.  The  ma- 
chines E  F  serve  to  excite  the  field  magnets  A  B  of 
generators  C  D,  and  the  intensity  of  magnetization  is 
governed  by  the  speed  of  revolution  of  E  F  and  the 
amount  of  resistance,  O,  interposed  in  their  circuits. 

The  hydraulic  piston  mechanism  of  Fig.  84  acts  posi- 
tively in  both  directions,  the  piston  moving  up  or  do.wn 
accordingly  as  water  is  admitted  to  one  end  or  the  other 
of  the  cylinder.  The  supply  of  water  is  by  way  of  the 
pipes  U,  and  its  waste  is  through  pipes  V ;  magnets  T 
T  operate  the  two  sets  of  valves.  The  piston-rod  X  has 
three  distinct  functions :  firstly,  through  suitable  mecha- 
nism it  regulates  the  supply  of  steam  in  connection  with 
the  governor  of  the  driving  engine  ;  secondly,  by  means 
of  resistances,  O,  in  the  circuit  of  the  exciting- machine  it 
varies  the  intensity  of  the  field  of  force  of  the  gene- 
rators C  D  ;  and,  thirdly,  it  connects  the  generator  B 
in  circuit  when  the  requirements  of  the  circuit  become 
greater  than  the  capacity  of  generator  C,  and  vice  versa. 


GENERAL  DISTRIBUTION.  155 

The  contact-arm  N  serves  to  vary  the  magnetic  inten- 
sity of  generators  C  D  by  changing  its  position  of  con- 
nection with  the  insulated  contact-plates  M.  The  pins 
Q  Q,  insulated  from  the  piston-rod  by  collars  P,  serve 
to  introduce  and  remove  generator  D  from  circuit  by 
changing  the  position  upon  blocks  S  S'  of  the  sliding 
connections  R  R'.  When  the  connections  R  R'  are  in 
the  position  shown,  the  circuit  of  the  distributing  mains 
is  from  connection  R'  to  stud  S'2  and  generator  D;  thence 
through  generator  C,  and  relay-magnet  Gr,  to  the  system 
of  lamps  Z  ;  thence  by  way  of  stud  S'g  to  connector  R/. 
The  circuit  of  the  exciting-machines  is  from  connection 
R  to  stud  S8 ;  thence  through  exciting-machine  F,  the 
coils  of  magnets  B  and  A  and  exciting-machine  E  to  the 
lower  regulator-plate  M^ ;  and  thence  by  way  of  resis- 
tances O  to  another  plate,  M,  the  connecting-arm  IS",  and 
stud  S2  to  the  connection  R.  The  amount  of  current 
flowing  through  the  coils  of  relay -magnet  G  is  propor- 
tioned by  an  adjustable  resistance  Y.  As  lamps  are 
added  to  the  circuit  of  the  main  the  arm  N  falls,  and  by 
thus  removing  resistance  from  the  circuit  of  the  exciting- 
machines  the  intensity  of  the  field  of  force  of  the  gene- 
rators is  increased,  and  more  current  is  supplied  to  the 
mains.  When  lamps  are  removed  from  the  main  by 
short-circuiting  them,  there  being  less  resistance  in  the 
main  and  correspondingly  less  current  required,  the  arm 
N  rises,  and  the  fields  of  force  are  weakened  ;  and  when 
the  requirements  of  the  circuit  are  reduced  to  the  capa- 
city of  a  single  generator,  the  pins  Q  Q'  throw  the  con- 
nections R  R7  upon  the  pieces  S  S',  Nos.  1  and  2  ; 
generator  D  and  exciting-machine  F  are  removed  from 


156  ELECTRIC  LIGHTING  BY  INCANDESCENCE. 

the  circuit,  and.  power  is  no  longer  expended  in  driving 
them.  The  arm  N  falls  to  a  point  upon  the  plates  M  at 
which  the  intensity  of  the  field  of  force  of  generator  C  is 
maintained  at  the  proper  intensity.  The  galvanic  bat- 
tery K  actuates  the  valve  mechanism  of  magnets  F  F', 
according  as  lever  H  establishes  connection  with  contact- 
screw  I  or  J. 

Such  a  system  of  regulation,  it  will  readily  be  seen,  is 
of  indefinite  variability,  and  it  is  apparent  that,  disre- 
garding the  one  element  of  friction,  the  power  expended 
in  the  production  of  current  is  almost  proportional  to 
the  value  of  the  current  produced. 

The  proper  construction  of  the  distributing-mains  is  a 
matter  of  great  importance,  and  it  is  not  likely  that  the 
best  construction  will  be  found  without  the  aid  of  prac- 
tical experience.  In  insulating  qualities  the  degree  of 
perfection  of  telegraphic  conductors  need  not  be  expected 
and  should  not  be  required.  The  mains,  especially  in 
cities,  should  be  laid  under  ground  ;  otherwise  the  liabi- 
lity of  interruption  is  considerable.  With  an  insulated 
copper  conductor  enclosed  in  an  iron  tube,  the  construq- 
tion  is  efficient,  compact,  and  simple  ;  and  all  that  re- 
mains to  be  done  is  to  protect  the  iron  from  oxidization, 
and  bury  the  whole  well  under  the  surface  of  the  earth. 
At  the  central  station  the  insulated  conductor  is  connect- 
ed to  one  pole  of  the  generating  apparatus,  to  the  other 
pole  of  which  the  enclosing-tube  is  connected.  At  the  ter- 
minus of  the  main  the  enclosing-tube  and  the  insulated 
conductor  are  connected  together.  Thus  the  circuit  of 
the  main  is  from  the  generating  apparatus,  by  way  of  the 
copper  conductor,  to  the  distant  end  of  the  main,  and 


GENERAL   DISTRIBUTION.  157 

thence  by  way  of  the  enclosing-tube  back  to  the  gene- 
rating apparatus.  The  tube  being  of  iron,  its  mass  per 
foot  of  length  should  be  seven  times  that  of  the  enclosed 
copper  conductor. 

In  order  to  divert  the  current  at  any  point  along  the 
route,  the  main  is  cut,  and  its  ends  enter  the  sides  of  a 
metal  box  provided  with  a  removable  cover.  By  means  of 
ordinary  elbow- joints  each  end  of  the  copper  conductor 
is  connected  with  an  insulated  branch  conductor  at  right 
angles  to  it,  which  branches  are  also  enclosed  in  a  tube 


Pig.  88.  Underground  Main  and  Branch. 

entering  the  box  (Fig.  88).  After  the  connection  is 
made  the  box  is  sealed  by  filling  it  with  any  insulating 
cement  impervious  to  moisture. 

By  means  of  improved  machinery  the  manufacture  of 
insulated  conductors,  suitable  for  the  purposes  of  elec- 
tric lighting,  has  been  made  commercially  successful. 
We  shall  not  attempt  to  decide  the  respective  merits  of 
the  methods  employed,  whose  efficiency  will  be  best  de- 
termined by  experience  and  after  long-continued  use. 
One  of  the  recent  improvements,  devised  by  Prof.  Eaton, 


158 


ELECTKIC  LIGHTING  BY  INCANDESCENCE. 


consists  in  passing  the  copper  wire  through  an  insulat- 
ing material  in  a  viscous  state,  and  thence  through  a 
tube  around  the  mouth  of  which  a  stream  of  melted  lead 
is  caused  to  flow  (Fig.  89).  The  insulating  material  is 
contained  in  the  cavity  A,  and  the  molten  lead  in  the 
chamber  B.  The  flow  of  lead  through  the  annular  space 
between  the  opening  in  the  chamber  B  and  the  mouth  of 
the  tube  C  is  produced  by  the  pressure  of  a  steel 
plunger,  D,  operated  by  an  hydraulic  press.  The  result 
is  a  compact  and  perfect  covering  of  lead  around  the  in- 


Fig.  89.  Apparatus  of  Prof.  Eaton. 

sulated  conductor ;  and  it  does  not  appear  that  there  is 
any  immediate  limit  to  the  number  of  separate  insulated 
strands  of  copper  that  may  be  thus  enclosed  in  a  single 
tube,  although,  in  the  manufacture  by  Prof.  Eaton, 
thus  far  only  seven  strands  have  been  insulated. 

The  questions  which  arise  regarding  the  limit  of  ex- 
tension of  any  distributing  system  cannot  yet  be  an- 
swered in  a  satisfactory  manner.  To  operate  from  one 
station  ten,  fifty,  or  one  hundred  thousand  lamps  may 
be  considered  a  mere  matter  of  engineering  skill,  but  the 
limit  of  the  capability  for  extension  of  any  system  must 


GENERAL  DISTRIBUTION.  159 

be  decided  by  considerations  of  cost  and  practicality. 
If  the  lamps  to  be  operated  are  distributed  over  a  sec- 
tion such  as  would  be  included  in  a  circle  one  mile  in 
diameter,  with  the  generating  station  located  at  a  central 
point,  there  may  be  said  to  be  no  real  difficulties  in  the 
way ;  but  when  we  attempt  to  extend  the  lighting  area 
the  questions  of  cost  then  arising  are  not  easily  met,  and 
in  turning  from  them  we  are  brought  face  to  face  with 
questions  of  practicability.  The  resistance  of  a  circuit 
external  to  the  lamps  and  generators  is  in  the  mains  ;  and 
in  order  that  current  may  be  conveyed  with  a  minimum 
of  loss,  it  is  necessary  that  the  resistance  of  the  mains 
shall  be,  if  not  nil,  at  least  inconsequential.  If  we  double 
the  radius  of  a  distributing  system,  we  must  double  the 
length  of  each  main  ;  and  in  order  that  the  resistance  of 
the  mains  shall  not  be  increased,  we  must  double  the 
mass  of  metal  composing  them.  Thus  we  quadruple  the 
cost.  It  is  true,  also,  that  we  quadruple  the  number  of 
mains  in  order  to  cover  the  quadrupled  area ;  but  this 
should  not  properly  be  taken  into  consideration,  for  it  is 
assumed  that  only  the  same  number  of  lamps  is  operated 
upon  each  main  in  the  enlarged  as  in  the  original  sec- 
tion, and  that  all  the  mains  radiate  in  sensibly  straight 
lines  from  the  distributing  station.  Increasing  the  ra- 
dius of  lighting  area  to  two  miles  again  quadruples  the 
cost  of  each  main ;  so  that  it  appears  that  the  cost  of 
mains  alone,  necessary  to  conduct  the  current  for  a  given 
number  of  lamps,  is  sixteen  times  greater  when  the  dis- 
tance from  the  distributing  station  to  the  most  remote 
lamp  is  two  miles  than  when  it  is  but  half  a  mile.  For 
this  reason  it  is  extremely  improbable  that  the  transmis- 


160  ELECTRIC  LIGHTING  BY  INCANDESCENCE. 

sion  of  electricity  to  any  great  distance  will  ever  be  at- 
tempted. 

If  it  were  possible  to  increase  the  delivering  capacity 
of  a  conductor  indefinitely  by  increasing  the  electro-mo- 
tive force  of  the  current,  it  might  be  practicable  to  con 
vey  the  power  of  Niagara  Falls  to  the  Atlantic  seaboard ; 
and  if  it  were  possible  to  devise  any  arrangement  for 
using  the  current,  it  would  be  possible  there  to  utilize  it 
in  the  production  of  light  in  electric  lamps  and  power  in 
electric  engines.  We  have  already  had  occasion,  in  de- 
scribing the  connection  of  electric  lamps  in  series,  to 
speak  of  the  difficulties  of  insulation.  To  convey  the 
current  of  a  thousand  horse-power  a  distance  of  one 
mile  through  a  copper  conductor  one-quarter  of  an 
inch  in  diameter  would  involve  a  high  degree  of  per- 
fection of  insulation  in  the  conductor,  and  the  conse- 
quences in  loss  of  life  from  accidental  diverting  of  the 
current  through  the  person  between  the  generator  and 
the  mile  terminus  would  be  such  as  to  prevent  its  em- 
ployment in  any  community.  To  extend  the  conductor 
a  distance  of  five  hundred  miles,  involving  an  increase  in 
electro-motive  force  of  current  of  five  hundred  times,  and 
an  increase  in  the  cost  of  the  conductor  of  five  hundred 
times,  would  be  to  magnify  the  error,  the  danger,  and 
the  impracticability  five  hundred  times.  No  generator 
or  series  of  generators  which  would  not  short-circuit  the 
current  within  themselves  could  ever  be  devised. 

The  cost  of  a  quarter-inch  copper  conductor  laid  and 
insulated  for  ordinary  currents  is  about  $1,350  per  mile  ; 
for  a  distance  of  500  miles  its  cost  would  be  $660,000, 
and  the  cost  of  maintenance  would  be  per  annum— 


GENERAL  DISTRIBUTION.; 

Depreciation  at  5  per  cent.,  .        .        .     $33,000 
Interest  on  investment  at  7  per  cent.,  .      46,200 

Total,  .        .        .        .     '   .        .     $79,200 

Leaving  out  of  consideration  the  cost  of  maintenance 
of  water-power  and  the  wear  and  tear  of  electric  genera- 
tors, and  considering  only  the  cost  of  steam-power  in 
large  engines,  which  may  be  stated  as  four-fifths  of  a 
cent  per  hour  per  horse-power,  we  are  led  to  the  conclu- 
sion that  the  cost  of  local  steam-power  is  less  than  would 
be  the  cost  of  these  long  insulated  conductors  alone. 

A  necessary  adjunct  of  any  general  distributing  sys- 
tem is  the  electric  metre,  an  instrument  designed  to  re- 
cord or  indicate  the  amount  of  current  consumed.  Seve- 
ral methods  of  measurement  have  been  devised,  the  most 
simple  of  which  is  the  invention  of  Mr.  Edison  (Fig.  90). 


Fig.  90.  The  Edison  Metre. 

The  Edison  metre  is  based  upon  the  principles  of  elec- 
trolysis. A  fractional  part  of  the  current  supplied  to 
the  circuit  of  a  lamp,  B,  is  diverted  to  a  bath,  A,  of  sul- 
phate of  copper  in  solution  by  way  of  the  electrodes 
D  E.  The  proportion  of  current  thus  diverted  is  regu- 
lated by  an  artificial  resistance,  C ;  and  in  order  to  de- . 


162 


ELECTRIC  LIGHTING  BY  INCANDESCENCE. 


termine  the  quantity  of  current  consumed  in  a  lamp  in 
any  period  of  time,  all  that  is  necessary  is  to  deduct  the 
weight  of  the  cathode  before  its  introduction  into  the 
bath  from  its  weight  after  removal  from  the  bath,  and  to 
multiply  the  remainder  by  the  number  of  times  the  re- 
sistance of  the  lamp-circuit  is  contained  in  the  resistance 
of  the  circuit  C  D  E,  the  electrolytic  action  of  unit  cur- 


Fig.  91.  The  Puller  Metre. 

rent  being  known.  For  the  R  of  B  being  1  ohm,  and  the 
R  of  C  D  E  being  1,000  ohms,  the  lamp  receives  •$-££}•  part 
of  the  current,  and  the  electrolytic  bath  yoVj  part.  By 
arranging  in  a  suitable  receptacle  a  sufficient  number  of 
the  baths  A,  each  connected  with  a  lamp,  the  value  of 
the  current  supplied  to  any  number  of  lamps  may  be 
accurately  determined. 

The  Fuller  metre,  designed  for  the  measurement  of 
alternating  currents,  is  shown  in  Fig.  91.     The  purpose 


GENERAL  DISTRIBUTION. 


163 


of  this  metre  is  to  automatically  register  the  number  of 
hours  during  which  a  lamp  is  operated.  Two  electro- 
magnets, so  wound  and  connected  as  to  produce  the 
polarities  indicated,  are  placed  in  the  circuit  of  the  lamp. 
A  polarized  steel  armature  playing  between  the  poles  of 
the  magnets  is  connected,  by  way  of  the  armature-lever, 
with  ratchet-and-pawl  mechanism.  Changing  in  polarity 
of  the  electro-magnets,  produced  by  the  alternating  cur- 
rents supplied  to  the  lamp,  serves  to  keep  the  armature 
in  vibration,  and  thus  to  rotate  a  train  of  registering 
wheels. 
The  Sawyer  metre,  Fig.  92,  is  also  a  time  metre.  It 


Fig.  92.  The  Sawyer  Metre. 

serves  to  register  the  time  during  which  a  lamp  is  in  use  ; 
and  since  the  unit  strength  of  current  and  the  require- 
ments of  the  lamp  are  known,  it  is  easy  to  determine  the 
value  of  the  current  used.  By  means  of  ratchet-and- 
pawl  mechanism  the  motion  of  the  armature  of  an  elec- 
tro-magnet is  communicated  to  a  set  of  dial-hands  which 
are  so  arranged  as  to  indicate  the  current  consump- 
tion or  the  candle-light  resulting  from  such  con- 
sumption. A  shaft,  E,  continuously  rotated  by  a  bi- 
weekly or  monthly  chronometer,  carries  two  insulated 


164  ELECTRIC  LIGHTING  BY  INCANDESCENCE. 

springs,  F,  which  are  in  electrical  connection  with  the 
coils  of  the  registering  magnet,  and  alternately  establish 
contact  with  the  opposite  pairs  of  pins,  A  A,  B  B,  C  C, 
D  D,  thus  diverting  a  small  fraction  of  the  current  sup- 
plied to  lamps  A'  B'  C'  D'  through  the  coils  of  the  mag- 
net, each  contact  of  the  springs  with  a  pair  of  pins  ener- 
gizing the  magnet  and  causing  the  ratchet-wheel  to  move 
one  tooth.  For  every  lamp  added  to  the  circuit  there  is 
an  additional  pair  of  pins.  If  only  one  lamp  is  in  use, 
the  springs  F  energize  the  magnet  but  twice  in  a  revolu- 
tion of  the  shaft ;  if  two  lamps,  four  times ;  if  all  the 
lamps  are  in  use,  the  ratchet-wheel  .is  kept  in  constant 


Fig.  93.  Edison's  Safety  Device. 

motion ;  therefore  the  record  of  the  dial-hands  is  as  ex- 
act when  one  or  two  are  in  use  as  when  any  other  num- 
ber of  lamps  is  in  use,  and  to  determine  at  any  time  the 
consumption  of  current  it  is  only  necessary  to  note  the 
position  of  the  dial-hands.  A  more  complete  metre,  to 
register  the  variations  of  current  consumed  in  each  lamp, 
has  been  devised,  and  finds  special  applicability  in  a 
series-multiple  system  ;  but  enough  has  been  written  to 
indicate  the  methods  of  measurement  that  are  most  like- 
ly to  come  into  use. 

To  preserve  the  continuity  of  a  circuit  in  case  of  acci- 
dent, and  to  obviate  the  dangers  of  short-circuiting, 
there  are  several  devices  of  about  equally  practical  ap- 
plication. In  the  Edison  system  of  distribution  obvia- 


GENERAL  DISTRIBUTION. 


165 


tion  of  a  short-circuit  is  the  one  thing  necessary,  and  to 
this  end  a  section  of  the  circuit  of  a  lamp  is  composed 
of  a  small  conductor  (Fig.  93),  which  under  ordinary 
circumstances  is  unaffected,  but  which,  when  there  is  an 
abnormal  flow  of  current,  is  instantly  fused.* 

To  the  same  end  we  have  the  Sa^er-Man  Safety- 
Switch  (Fig.  94),  operating  as  follows:  The  current,  in 
traversing  a  branch,  enters  by  way  of  a  broad,  flat 
spring  and  a  lever  whose  movement  is  stopped  by  a 
projection  on  the  end  of  the  armature-lever  of  an  electro- 


Fig.  94.  Sawyer-Man  Safety-Switch. 

,  magnet  included  in  the  circuit.  When  the  flow  of  cur- 
rent through  the  branch  is  normal,  the  magnetic  force 
developed  is  insufficient  to  move  the  armature,  and  thus 
to  release  the  lever  ;  but  when,  from  any  cause,  there  is 

*  In  Mr.  Edison's  description  of  this  appliance  he  says  :  "  This  small 
conductor  has  such  a  degree  of  conductivity  as  to  readily  allow  the  passage 
of  the  amount  of  current  designed  for  its  particular  branch,  but  no  more. 
If,  from  any  cause  whatever,  an  abnormal  amount  of  current,  large  enough 
to  injure  the  translation  devices  or  to  cause  a  waste  of  energy,  is  diverted 
through  a  branch,  the  small  safety-wire  becomes  heated  and  melts  away, 
breaking  the  overloaded  branch-circuit.  It  is  desirable,  however,  that  the 
few  drops  of  hot  molten  metal  resulting  therefrom  should  not  be  allowed  to 
fall  upon  carpets  or  furniture,  and  also  that  the  small  safety-conductor 
should  be  relieved  of  all  tensile  strain;  hence  I  enclose  the  safety-wire  in  a 
jacket  or  shell  of  non-conducting  material,  which,  preferably,  is  screwed  to 
the  ends  of  the  large  conductors,  uniting  them,  not  electrically,  but  as  to 
tensile  strain." 


166 


ELECTRIC  LIGHTING  BY  INCANDESCENCE. 


an  excessive  flow  of  current  through  the  branch,  the  ar- 
mature is  attracted  beyond  the  force  of  its  retracting 
spring,  and  the  lever  through  which  we  obtain  the  cir- 
cuit is  released,  and  thus  the  circuit  of  the  overloaded 
branch  is  broken. 

In  the  Brush  and  the  Sawyer  systems  preservation 
of  the  continuity  of  the  circuit,  rather  than  its  automatic 
interruption,  is  the  end  sought.  In  the  Brush  system 
the  circuit  is  through  the  lamp  and,  by  way  of  a  shunt, 
through  the  coils  of  an  electro-magnet,  whose  armature- 
lever  operates  to  short-circuit  the  lamp  when  the  circuit 


Fig.  95.  Circuit-Preserving  Magnet. 

of  the  lamp  is  interrupted.  In  the  Sawyer  system  the 
circuit  is  first  through  the  coils  of  an  electro-magnet  and 
then  through  the  lamp,  and  when  the  circuit  is  inter- 
rupted the  armature-lever,  being  no  longer  attracted, 
falls  and  establishes  a  short-circuit  around  the  lamp 
(Fig.  95). 

The  Sawyer  differential  magnet  device  (Fig.  96)  has 
special  application  in  a  series-multiple  system  of  distri- 
bution. The  circuit  from  the  -|-  point  is  a  diviHed  one, 
one-half  of  the  current  flowing  in  one  direction  around 
the  core  of  magnet  A,  and  the  other  half  flowing  in  the 
opposite  direction  around  the  core,  the  divided  circuit, 
including  the  lamps  I,  uniting  and  terminating  at  the  — 


GENERAL  DISTRIBUTION. 


167 


point.  Thus,  when  the  circuit  of  each  lamp  is  perfect, 
the  magnetism  in  magnet  A,  developed  by  the  current 
flowing  in  the  circuit  of  one  lamp,  is  neutralized  by  the 
magnetic  effects  of  the  current  flowing  in  the  circuit  of  the 
other  lamp,  and  armature  B,  attached  to  lever  C  (which 
is  pivoted  at  D  and  ordinarily  retracted  by  spring  E  to  a 
contact  with  stop-pin  F),  is  unaffected.  When,  however, 


Fig.  96.  Automatic  Differential  Magnet  Switch. 

an  interruption  of  either  circuit  occurs,  the  neutralizing 
magnetic  influences  of  the  current  upon  the  magnet  A 
no  longer  exist,  armature  B  is  attracted  by  the  magnet 
A,  and  by  way  of  contact  face-plates  Gr  one-half  of  the 
current  is  diverted  to  the  artificial  resistance  H.  In  case 
of  interruption  of  the  circuit  of  the  other  lamp,  the  en- 
tire current  passes,  by  way  of  the  core  of  magnet  A  and 
contact-plates  Gf,  through  the  resistance  H. 


CHAPTER  XII. 

COMMERCIAL    ASPECTS. 

light  of  an  incandescent  lamp  has  been  shown  to 
be  suitable  in  every  respect  for  domestic  use.  Its 
characteristics  are  the  characteristics  of  daylight.  In 
steadiness  it  is  comparable  only  to  the  light  of  the  sun. 
No  other  artificial  light,  not  excepting  that  of  the  best 
Argand  burner,  is  as  steady.  This  is  not  only  true  of 
the  Sawyer  lamp,  but  of  all  other  lamps  in  which  com- 
bustion of  the  carbon  is  prevented  ;  and  when  carbon  is 
raised  to  the  temperature  of  limpid  incandescence,  there 
is  no  difference  between  the  light  evolved  and  that  which, 
proceeding  from  the  sun,  is  diffused  and  softened  by  the 
stratum  of  air  it  traverses.  The  heat  radiated  is  much 
less  than  that  of  gas-light  of  equal  power.  The  noxious 
vapors  proceeding  from  the  combustion  of  illuminating 
gas  disappear.  No  chemical  action  takes  place,  but  her- 
metically sealed  in  its  crystal  chamber,  protecting  from 
danger  of  fire  and  explosion,  a  fragment  of  carbon  glit- 
ters and  glows,  rises  to  the  light  of  a  taper,  brightens 
and  broadens,  and  finally  illuminates  with  the  effulgence 
of  day.  This  is  what  the  incandescent  light  should  be, 
and  what  it  is  under  proper  conditions. 

There  being  no  question  as  to  the  adaptability  of  this 
new  illuminant  to  all  the  purposes  of  interior  illumina- 


COMMERCIAL  ASPECTS. 

tion,  the  other  and  most  important  question  that  arises 
is  one  of  economy.  Is  this  light,  which  is  better  than 
gas-light,  as  cheap  as,  or  cheaper  than,  gas-light? 

In  the  experiments  at  the  South  Foreland  light-house, 
conducted  by  Prof.  T  yndall,  it  was  shown  that  the  new 
Siemens  or  Hafner-Alteneck  machine  developed  a  fraction 
over  900  candle-light  per  horse-power  expended  in  driv- 
ing it,  and  in  one  case  1,254  candle-light.  We  will  take 
the  minimum  accomplishment  as  a  safe  basis  for  our  cal- 
culations. 

In  the  best  steam-engines  the  consumption  of  coal  per 
hour  per  horse-power  is  two  pounds,  costing,  at  five  dol- 
lars per  ton,  one-half  cent.  One  pound  of  coal  yields 
five  cubic  feet  of  gas,  and,  therefore,  the  cost  of  one 
cubic  foot  of  gas  is  one-twentieth  of  one  cent.  To  pro- 
duce the  light  of  450  candles  by  the  Hafner-Alteneck 
machine  involves  the  consumption  of  one  pound  of  coal, 
costing  one- quarter  cent.  To  produce  equivalent  light 
from  gas,  at  a  rate  of  consumption  of  five  cubic  feet  per 
15  candle-light,  we  must  burn  150  cubic  feet,  and  the 
cost  of  production,  at  one-  twentieth  of  a  cent  per  cubic 
foot,  or  fifty  cents  per  thousand,  is  seven  and  one-half 
cents.  Thus  the  cost  of  the  electric  light  is,  as  to  fuel- 
consumption,  but  one-thirtieth  the  cost  of  gas-light ;  but 
there  is  an  advantage,  in  the  respect  of  coke  recovered  in 
the  retort,  in  the  case  of  gas,  which  may  be  said  to  in- 
crease the  cost  of  electric  light  to  one-fifteenth  the  cost 
of  gas-light. 

One  cubic  foot  of  coal-gas  equals  690  heat-units,  or 
532,680  foot-pounds,  and  five  cubic  feet  equal  2,663,400 
foot-pounds.  One  horse-power  equals  1,980,000  foot- 


170  ELECTRIC  LIGHTING  BY  INCANDESCENCE. 

pounds.  The  five  cubic  feet  of  gas,  burned  in  the  boiler 
of  a  steam-engine  recovering  ten  per  cent,  of  the  energy 
conserved  in  the  gas,  will  yield  in  mechanical  force 
yiW&WV  horse-power,  which  would  develop  in  the  elec- 
tric lamp  a  light  of  120  candles.  Burned  in  a  gas-burner, 
it  develops  but  15  candle-light.  Therefore  it  is  cheaper 
to  convert  coal  into  gas,  and  the  gas  into  steam-power, 
and  the  steam-power  into  electricity,  and  the  electricity 
into  light,  than  it  is  to  produce  light  by  the  direct  con- 
sumption of  gas. 

In  this  it  will  be  noted  that  the  cost  of  lighting  by  the 
voltaic  arc  is  alone  considered.  We  have  now  to  com- 
pare with  this  cost  the  cost  of  lighting  by  incandes- 
cence. 

The  tests  of  the  Konn  and  Bouliguine  lamps,  made  by 
M.  Fontaine,  gave  a  development  of  eighty  Carcel  burn- 
ers from  the  current  which  in  an  arc  lamp  produced  a 
light  of  one  hundred  burners.  Our  own  experiments, 
with  pencils  heated  to  intense  incandescence,  have 
shown  a  development  of  but  seventy  per  cent.,  as  against 
eighty  per  cent,  recovered  by  M.  Fontaine.  In  order 
that  the  lamp  may  be  lasting,  however,  the  development 
from  the  same  current  should  not  much  exceed  fifty  per 
cent,  of  the  light  of  the  arc.*  Thus,  light  by  incandes- 
cence is  twice  as  costly  as  light  by  the  voltaic  arc  ;  hence 
it  may  be  stated  that,  taking  the  estimates  above  given, 
the  cost  of  incandescent  lighting  is  about  one-seventh  the 
cost  of  gas -lighting. 

*  We  have  shown  in  Chapter  III.  a  development  by  incandescence  of  275 
candle-light  from  the  current  which,  in  the  voltaic  arc,  yielded  a  light  of 
500  candles. 


COMMERCIAL  ASPECTS  171 

In  the  estimate  of  cost  of  the  voltaic-arc  light,  we  have 
not  included  the  consumption  of  carbon  in  the  lamp,  for 
the  reason  that  in  incandescent  lamps  the  carbon  is  pre- 
served from  consumption  ;  and  we  have  only  introduced 
the  subject  of  voltaic-arc  lighting  in  order  to  exhibit 
the  verified  results  obtained  by  Professor  Tyndall  and 
others. 

We  have  not  yet  considered  the  cost  of  plant  or  the 
cost  of  attendance  in  either  the  gas  system  or  the  elec- 
tric system  of  lighting,  and  we  have  allowed  but  50  cents 
per  thousand  cubic  feet  as  the  cost  of  gas,  whereas  in 
New  York  City  the  average  cost  of  gas-production,  all 
items  of  expense  included,  is  70  cents  per  thousand,  and 
the  leakage  8  per  cent.,  while  the  cost  to  the  consumer  is 
$2  25  per  thousand. 

The  following  figures  relate  to  the  business  of  New 
York  gas  corporations : 

Capital  invested, $20,000,000 

Gross  sales  per  annum  (cubic  feet),  .        .     2,400,000,000 


Cost  of  gas  (70  cents  per  M.),    .        .        .  $1,680,000 

Interest  on  capital,  at  7  per  cent.,     .        .  1,400,000 

Taxes, 500,000 

Wastage  (8  per  cent.),       .        .        .        .  134,400 


Total,     (  .        ....        .        .        .         $3,714,400 

Gross  receipts,   ...        .        .        .  5,400,000 

Leaving  a  net  profit,  over  7  per  cent  upon  the  capital  in- 
vested, of  $1,700,000,  or  a  total  net  profit  of  15£  per 
cent. 


172  ELECTRIC  LIGHTING  BY  INCANDESCENCE. 

The  cost  of  lighting  has  almost  invariably  been  un- 
fairly stated  by  the  gas  interest  on  the  one  hand  and 
by  the  electric-light  interest  on  the  other.  The  state- 
ments of  the  former  have  been  based  upon  the  work- 
ing of  small  steam-engines,  and  the  cost  of  running 
them,  always  excessive,  and  the  cost  of  attendance, 
also  excessive  because  confined  to  a  limited  develop- 
ment of  light ;  whereas  with  large  steam-engines — en- 
gines of  500  horse-power  and  upward — the  cost  per  horse- 
power is  less  than  one  cent  per  hour.  Instead  of  taking 
the  cost  of  gas  as  the  basis  of  calculation,  the  electric- 
light  interest  has  considered  only  the  cost  to  the  con- 
sumer, which  is  no  more  to  be  considered  the  cost  than 
the  retail  price  of  any  production  is  to  be  considered  the 
cost  of  that  production.  Furthermore,  the  gas  interest 
has  invariably  urged  the  cost  of  the  conducting- wires  as 
an  insurmountable  obstacle  to  the  general  use  of  the 
electric  light,  basing  its  conclusions  upon  the  sizes  of  the 
wire  employed  in  special  uses  of  voltaic-arc  lamps  where 
the  utmost  utilization  of  the  current  developed  has  been 
attempted. 

In  no  case  will  the  cost  of  electric  mains  equal  the  cost 
of  gas  mains.  In  most  cases  it  will  fall  below  fifty  per 
cent,  of  the  cost  of  gas  mains.  In  no  case  will  the  cost 
of  branch  electric  conductors  equal  the  cost  of  branch 
gas  conductors. 

In  calculating  the  cost  of  electric  conductors,  the  fol- 
lowing table  will  be  found  of  use : 


COMMERCIAL   ASPECTS. 


173 


SIZE,  WEIGHT,  AND   RESISTANCE   OF    COPPER  WIRE.     SPECIFIC 
GRAVITY,  8.9. 


Diameter  in  decimal 
parts  of  an  inch. 

Weight  in  grains  per 
foot. 

Number  of  feet  per 
pound. 

Resistance  as  pure 
copper  at  60°  F.  in  ohms 
per  i  ,000  feet. 

I. 

21,159- 

.330828 

.010344 

.32573 

2,245. 

3.II803 

.097501 

•  134 

379-93 

18.425 

.576131 

.109 

25L37 

27.214 

.870786 

.083 

145.76 

48.023 

I.50I66 

.065 

89.397 

78.30 

2.4484 

.049 

50.803 

137.79 

4.3086 

•035 

25.920 

270.C6 

8.6416 

.028 

16.589 

421.97 

13.1951 

.025 

13.224 

529.38 

16.552 

Iron  wire,  galvanized,  in  order  to  have  tlie  same  con- 
ductivity as  copper  wire,  should  weigh  about  six  times 
as  much  as  copper  wire  per  foot.  The  resistance  of 
iron  wire  per  mile,  at  60°  Fahr.,  is,  in  ohms,  395,000 
divided  by  the  square  of  the  diameter  of  the  wire  in 
thousandths  of  an  inch.  The  weight  of  iron  wire  per 
mile  is  the  square  of  the  diameter  of  the  wire,  in  thou- 
sandths of  an  inch,  divided  by  72.15. 

The  resistance  of  iron  wire  increases  about  .0035  for 
each  degree  Fahr.  above  60°. 

The  resistance  of  copper  wire  increases  about  .0021  for 
each  degree  Fahr.  above  60°. 

The  question  of  transmitting  electricity  (continuous 
current)  to  a  distance  is  purely  one  of  resistance  of  the 
conductor ;  and  when  the  resistance  of  the  conductor 
leading  to  the  lamp-circuit  is  low  enough  to  permit  a 
satisfactory  per  cent,  realization  in  the  lamp-circuit, 
that  conductor,  whether  of  iron  or  copper  or  other 


174  ELECTBIC  LIGHTING  BY  INCANDESCENCE. 

metal,  and  whatever  its  size  or  cost,  is  all  that  is 
needed. 

We  have  shown  in  Chapter  IX.  that  in  a  series-mul- 
tiple system  of  10,000  lamps,  the  resistance  of  the  main 
conductor  may  be  as  high  as  one  ohm,  and  yet  permit 
the  utilization  as  light  of  eighty  per  cent,  of  the  current 
generated.  We  find  by  the  table  of  resistances  that  this 
conductor,  leading  a  distance  of  one  mile  from  the  sup- 
plying station  and  returning  thereto,  making  its  total 
length  two  miles,  would  be  substantially  fWAV  of  an 
inch  in  diameter,  or  less  than  one-third  of  an  inch.  As 
the  resistance  of  1,000  feet  of  this  conductor  is  .097501 
ohm,  the  resistance  of  two  miles  of  it,  or  10,560  feet, 
would  be  exactly  1.029  ohms.  The  cost  of  this  conduc- 
tor, as  copper  at  thirty  cents  per  pound,  would  be 
$1,016  10.  The  cost  of  a  copper  conductor,  one  mile  in 
length,  and  a  return  conductor  consisting  of  an  iron 
tube  of  equal  resistance  per  foot  length,  would  be  about 
$900.  Insulated  as  a  round  copper  wire,  one  mile  long, 
in  an  iron  enclosing-tube,  the  cost  would  be  about  $1,000, 
or  twenty  cents  per  foot.* 

But  here  we  are  brought  to  the  consideration  of  an- 
other question,  and  one  of  decided  importance — viz.,  the 
heating  of  the  conductor  by  the  current  traversing  it ;  for 
it  will  receive  and  waste  as  heat  one-twenty-lifth  as 
much  current  as  is  used  in  the  lamps,  or  the  heat  of  400 
lamps,  and  the  surface  of  the  outer  tube  exposed  to 
earth-conduction  is  not  sufficient  to  prevent  a  considera- 
ble rise  in  temperature,  with  consequent  waste  of  cur- 
rent, equivalent  to  leakage  in  a  gas  system.  As  much 

*  As  the  prices  of  metals  change  this  estimate  must  be  changed. 


COMMERCIAL  ASPECTS.  175 

heat  would  be  developed  in  each  section  of  the  conduc- 
tor thirteen  feet  long  as  would  be  developed  in  a  single 
lamp,  which,  although  small  in  itself,  owing  to  the  poor 
heat-conductivity  of  the  earth,  would  soon  appreciably 
increase  the  resistance  of  the  conductor.  In  order  to 
obviate  any  difficulty  from  this  source,  and  to  realize  a 
greater  economy  of  working,  it  is  well  to  increase  the 
size  of  the  copper  conductor  beyond  the  actual  require- 
ments— in  this  case,  say,  to  a  diameter  of  .65146  inch— 
and  thus  to  quadruple  its  conductivity  and  cost,  and  to 
increase  the  diameter  of  the  enclosing- tube  in  propor- 
tion. 

We  thus  reduce  the  resistance  of  the  main  to  .25  ohm, 
and  the  waste  of  current  to  that  of  100  lamps  ;  and  not 
only  is  the  lateral  cooling-surface  doubled,  but  the 
length  of  main  through  which  the  heat  of  a  single 
lamp  is  distributed  is  52.8  feet,  comparable  to  105.6  feet 
of  the  smaller  main.  The  result  is  that  the  very  slight 
heat  developed  by  the  current  is  dissipated,  and  there 
is  no  appreciable  increase  in  the  resistance  of  the  main. 
The  cost  of  such  a  main,  per  mile,  would  be  as  follows  : 

Copper,  at  30  cents  per  pound,  ....  $2,032 
Iron  tubing,  at  3  cents  per  pound,  .  .  .  1,026 
Insulation, 150 


Total  cost  of  electric  main,  per  mile,  .  .  $3,208 
€ost  of  eight-inch  gas  main,  at  3  cents  per* pound,  $6,660 

It  will  thus  be  seen  how  little  foundation  there  is  for 
the  absurd  estimates  from  time  to  time  published  con- 
cerning the  cost  of  electric  conductors.  By  reference  to 


176  ELECTRIC  LIGHTING  BY  INCANDESCENCE. 

the  table  of  resistances,  the  reader  may  accurately  deter- 
mine  the  cost  of  the  main  necessary  for  any  number  of 
lamps,  and  the  percentage  of  waste  in  the  same.  In  the 
case  of  a  system  of  10,000  lamps,  the  waste  of  current 
in  the  mains  is  almost  exactly  one  per  cent.,  while  the 
leakage  of  a  New  York  gas  system  is  eight  per  cent. 

By  far  the  greater  portion  of  the  plant  of  a  gas  system 
is  in  poorly-paying,  or  comparatively  poorly-paying,  dis- 
tricts. In  the  lighting  of  houses  where  very  little  gas  is 
used,  and  in  large  sections  of  border  territory,  there  is 
but  little  and  sometimes  no  profit.  The  profits  of  a  gas 
system  are  in  the  lighting  of  factories  and  large  business 
houses,  stores  and  hotels,  halls  and  theatres,  and  the 
wealthier  parts  of  a  city  where  the  most  of  the  gas  pro- 
duced is  consumed.  The  area  of  New  York  City  is  about 
sixteen  square  miles,  but  the  most  profitable  territory 
would  be  within  the  lighting  area  of  eight  electric  sta- 
tions, each  covering  one  square  mile  of  territory. 

In  all  places  where  power  already  exists,  the  cost  of 
electric  lighting  is  the  cost  of  the  extra  coal  consumed 
in  the  engine,  interest  upon  the  investment  in  lamps 
and  generators,  and  the  cost  of  occasional  renewal  of  the 
lamps. 

If  electric  lighting  by  incandescence  is  as  cheap  as,  or 
cheaper  than,  gas  lighting,  a  comparison  of  the  cost  of 
operating  a  gas  system  with  the  cost  of  operating  an 
electric  lighting  system  will  demonstrate  the  fact.  If 
electric  lighting  by  incandescence  is  the  more  costly,  the 
comparison  will  demonstrate  that  fact. 

We  will  take  a  section  of  four  square  miles  of  New 
York  City,  from  the  better-paying  portion  of  the  city. 


COMMERCIAL  ASPECTS.  177 

Thus  it  will  be  as  favorable  for  gas  lighting  in  propor- 
tion as  the  better-paying  portion  of  any  city  is  favor- 
able for  gas  lighting.  And  it  will  be  favorable  for 
electric  lighting  as  it  is  favorable  for  gas  lighting. 

We  will  first  consider  the  cost  of  the  gas  system. 

The  investment  in  the  gas  plant  for  sixteen  square 
miles  of  territory  is  $20,000,000,  as  already  shown.  The 
investment  for  four  square  miles,  where  there  is  the 
largest  consumption  of  gas,  is  more  than  one-fourth  of 
this  amount,  for  the  cost  of  the  mains  is  greater,  and  the 
cost  of  machinery  and  real  estate  is  very  much  greater,  in 
proportion.  We  will  consider  the  investment  as  $6,000,- 
000,  and  the  gas-production  as  4,000,000  cubic  feet  per 
day.  The  cost  of  operating  this  system  per  annum  is 
as  follows  : 

Interest  on  investment,  at  7  per  cent,       .        .  $420,000 
Gas-production,  1,460,000,000   cubic  feet  per 
annum,  at  70  cents  per  M.,  which  is  inclu- 
sive of  all  connected  expenses,     .        .        .  1,022,000 
Wastage  of  gas,  at  8  per  cent.,        .        .        .  81,760 

Taxes, 150,000 

Depreciation  of  plant,  at  5  per  cent.,       .        .  300,000 


Total  cost  per  annum,        ....  $1,973,760 
Gross  sales  (wastage  deducted),  1,343,200,000. 

cubic  feet,  at  $2  25  per  M,    .        .        .         .  $3,022,200 
Profit  over  7  per  cent,  on  capital,    .        .        .    1,048,440 

Deducting  8  per  cent,  leakage  from  the  4,000,000  cubic 
feet  of  gas  used  per  day  leaves  3,680,000  cubic  feet  util- 


178  ELECTRIC  LIGHTING  BY  INCANDESCENCE. 

ized  in  light-production,  which  would  allow  an  average 
use  of  184,000  5-foot  burners  four  hours  daily.  We  are 
to  compare  this  consumption  of  gas  in  gas -lighting  with 
steam-power  consumption  in  electric  lighting  ;  and  as  in 
the  new  development  of  electric  lighting  we  do  not  con- 
sume power  except  as  light  is  needed,  and  as  more  or  less 
light  is  needed  throughout  the  twenty-four  hours  of  each 
day,  we  may  employ  almost  any  number  of  hours  as  the 
basis  of  calculation.  Taking  the  high  average  of  12  can- 
dle-light per  burner  [see  Edgerton's  certificate,  Chapter 
VII.],  we  find  that  the  total  light  obtainable  from  184, 000 
burners  is  2,208,000  candles.  These  burners  are  not  dis- 
tributed among  184,000  different  apartments,  but  there 
are,  say,  1,000  apartments,  as  stores,  dining-rooms,  etc., 
averaging  30  burners  each,  1,000  averaging  10  burners 
each,  10,000  averaging  4  burners  each,  15,000  of  2  burn- 
ers each,  and  74,000  of  1  burner  each,  distributing  the 
light  among  101,000  apartments.  It  may  be  said  that  at 
certain  hours  there  are  more  than  101,000  separate  apart- 
ments lighted,  and  at  other  hours  less.  This  is  true,  but 
the  electric-lighting  system,  which  consumes  power  in 
proportion  to  the  requirements  of  the  system,  is  capable 
of  expanding  and  contracting  the  supply  of  electricity, 
just  as  the  gas  system  is  capable  of  expanding  and  con- 
tracting the  supply  of  gas,  and  just  as  economically.  It 
costs  less  to  get  100  horse-power  out  of  an  engine  capable 
of  developing  200  horse-power  than  it  costs  to  get  100 
horse-power  out  of  a  100  horse-power  engine. 

In  another  chapter  we  have  explained  the  economy 
of  incandescent  lamps  of  large  foci  as  compared  with 
those  of  small  foci.  Thus  the  current  generated  by  the 


COMMERCIAL  ASPECTS.  17$ 

expenditure  of  from  one-half  to  one  horse-power  produces 
in  a  single  lamp  a  light  of  275  candles  ;  the  mirrent  gene- 
rated by  one  horse-power  produces  in  two  lamps  in  series 
a  light  of  120  candles  per  lamp  ;  in  three  lamps,  60  candles 
per  lamp ;  in  four  lamps,  30  candles  per  lamp ;  in  five 
lamps,  from  10  to  15  candles  per  lamp  ;  the  increasing 
external  resistance  and  the  greater  percentage  of  current 
utilized  as  light,  together  with  the  easier  motion  of  the 
generator,  when  the  number  of  lamps  is  increased,  ac- 
counting for  the  proportions  given. 

In  order  to  supplant  the  184,000  5-foot  burners  of  the 
gas  system,  we  must  employ  103, 000  electric  burners,  dis- 
tributed and  requiring  power  to  operate  as  shown  in  the 
following  table  (page  180),  which  also  shows  the  distribu- 
tion, power,  and  consumption  of  gas-burners. 

It  will  be  noted  that  these  figures  are  not  founded  upon 
a  realization  of  from  10  to  20  lights,  of  16  candle-power 
each,  per  horse-power  of  force  expended  in  driving  the 
generator,  but  upon 

2  lamps  of  120  candle-power,  or 

3  lamps  of    60  candle-power,  or 

4  lamps  of    30  candle-power,  or 

5  lamps  of  10  to  15  candle-power. 

In  further  division  there  is  great  loss.  We  have  never 
obtained  more  than  17  lights  of  12  candle-power  each  per 
three  horse-power,  and  this  only  in  laboratory  experi- 
ments under  favorable  conditions  ;  nor  can  very  much 
more  ever  be  obtained  from  magneto  or  dynamo-electric 
generators.  Further  economical  division  is  to  be  looked 


180  ELECTRIC  LIGHTING  BY  INCANDESCENCE. 


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COMMERCIAL  ASPECTS. 

for  through  increased  efficiency  of  steam-engines  or  other 
mechanical  powers. 

In  lamps  of  large  foci  we  find  the  greatest  economy  ; 
but  it  is  apparent  that,  whether  we  operate  lamps  of  large 
foci  or  lamps  of  so  small  foci  as  10  to  15  candle-power, 
the  cost  of  the  electric  light  is  less  than  the  cost  of  gas- 
light, with  gas  at  seventy  cents  per  thousand  and  steam- 
power  at  one  cent  per  hour  per  horse-power.  But  we 
will  now  consider  the  total  cost  of  plant  and  operating 
and  maintaining  an  electric-lighting  system  equalling 
in  light- production  a  gas  system  using  3,680,000  cubic 
feet  of  gas  per  day. 

The  following  is  the  investment  per  station  supplying 
a  territory  of  one  square  mile : 

14  modern  steam-engines  of  500  horse-power 

each,       .        v       ,.iw  •;  .      .,  ,  ,   '  .V..  fi  .  .  $70,000 

Modern  improved  boilers  for  same,  .  .  50,000 

20  large  dynamo-electric  machines,  .  .  80,000 

Real  estate  and  appurtenances,         .  .  .  100,000 

25  miles  of  mains,  at  $3,000  per  mile,  .  .  75,000 

Laying  of  mains,  at  $1,500  per  mile,  .  .  37,500 


Total  per  station, $412,500 

Pour  stations,  with  plant  complete,         .         .  $1,650,000 

Total  horse-power, 28,000 

The  operating  expenses  of  each  station  per  day  would 
l>e  as  follows  : 

1  chief -engineer, $5  00 

2  assistant  engineers, 6  00 

3  second  assistant  engineers,  at  $2  50,     .        .  7  50 


182  ELECTRIC  LIGHTING  BY  INCANDESCENCE. 

8  stokers,  at  $1  50, $12  OO 

1  electrician, 5  00 

1  assistant, 2  00- 

40  tons  coal,  at  $4  35  in  bunkers,    .        .        .  174  00 

Oil,  waste,  etc.,          .  10  00 


Total  per  day, $221  50 

Total  for  four  stations,       ....      $886  00 

These  engines  would  consume  two  pounds  of  coal  per 
hour  per  horse-power,  which  for  four  hours'  run,  and  a 
development  of  6,000  horse-power  per  station,  would 
make  the  consumption  in  four  hours  24  tons  ;  but,  not- 
withstanding the  fact  that  the  consumption  is  in  almost 
direct  proportion  to  the  current  requirements,  we  have 
thought  best,  as  more  or  less  power  will  be  used  during 
the  entire  twenty -four  hours  of  the  day,  to  increase  the 
estimate  of  coal  consumption  66|  per  cent.  In  prac- 
tice the  consumption  would  fall  considerably  below  40 
tons,  but  we  have  in  all  cases  preferred  to  make  the  al- 
lowance excessive. 

The  mains  are  calculated,  not  from  centrally-located 
stations,  but  from  stations  located  upon  the  outskirts  of 
the  territory  to  be  supplied. 

We  have  not  yet  taken  into  consideration  the  cost  of 
renewal  of  the  electric  burner,  which  varies  according  to 
the  system  employed.  In.  the  Sawyer  lamp,  which  is  re- 
newed without  destroying  it,  the  cost  per  renewal  is  from 
eight  to  ten  cents.  The  average  frequency  of  renewal 
per  lamp  (combining  in  the  consideration  lamps  of  all 
foci)  is  once  in  three  to  four  months.  There  is  claimecL 
for  the  Edison  burner  a  life-time  of  six  months. 


COMMERCIAL  ASPECTS.  183 

In  recapitulating  the  cost  of  electric  lighting  per  sta- 
tion per  year,  we  obtain  the  following  result : 

Interest  on  investment,  at  7  per  cent.,  .        .  $28,875  00 
Depreciation  of  plant  (real  estate  and  ap- 
purtenances, and  mains),  at  5  per  cent.,    .  8,750  00 
Depreciation  of  engines,  boilers,  and  gene- 
rators, at  10  per  cent.,      .        .        iV       .  20,000  00 
Taxes,     .        .        .        .        .      .•".•.      •  10,31250 

Cost  of  operating,  at  $221  50  per  day,  .        .  80,847  50 
4  renewals  of  25,750  lamps,  at  10  cents  per 

renewal,      .         .        .        .        .        :  '  '•'.  10,30000 


Total  per  station,    .       ' '.-.       .        .        .    $159,08500 

Total  for  the  four  stations,    .      '.        .    $636,34000 

as  against  a  total  cost  per  annum  by  the  gas  system  of 

$1,973,760. 

At  a  rate  of  $1  12 J  per  thousand  for  gas,  the  gross  re- 
ceipts of  electric  lighting  would  be  $1,511,100,  or  a  net 
profit,  over  and  above  7  per  cent,  upon  the  capital  in- 
vested, of  $874,760,  or  a  total  net  profit  of  60  per  cent. 
To  be  as  cheap  as  electric  light,,  gas  must  be  manufac- 
tured, all  items  of  cost  and  management  included,  at  as 
low  a  rate  as  twenty-three  cents  per  thousand  cubic 
feet,  without  deduction  for  leakage.  We  have,  however, 
perhaps  overlooked  the  fact  that  while  from  the  gas  sys- 
tem we  obtain  a  total  light  of  2,208,000  candles,  we 
obtain  from  the  electric  system  a  total  of  2,455,000 
candles. 

In  order  that  the  matter  of  economy  may  be  made 
still  clearer,  let  it  be  assumed  that  we  can  accomplish 


184  ELECTRIC  LIGHTING  BY  INCANDESCENCE. 

but  fifty  per  cent,  of  what  is  shown  and  what  has  been 
done  with  the  electric  light — that  with  an  expenditure 
of  one  horse-power  we  can  only  obtain 

1  light  of  120  candle-power,  or 
1^  lights  of  60  candle-power,  or 

2  lights  of  30  candle-power,  or 
2J  lights  of  10  to  15  candle-power. 

The  cost  of  the  engines  and  boilers  would  be  dou- 
bled ;  that  of  the  generators  and  remainder  of  the 
plant  would  remain  as  before.  The  investment  would 
be  increased  from  $412,500  per  station  to  $532,500  per 
station,  and  the  cost  of  operating  (in  coal-consumption, 
etc.)  would  be  increased  from  $221  50  to  $415  50  per 
day.  The  table  of  cost  would  then  stand  as  follows  : 

Interest  on  investment,  at  7  per  cent.,          .  $37,275  00 
Depreciation  of  plant  (real  estate  and  ap- 
purtenances, and  mains),  at  5  per  cent.,      .  8,75000 
Depreciation  of  plant  (engines,  boilers,  and 

generators),  at  10  per  cent.,         .,     v  *        .  32,000  00 

Taxes,     ,.,:,.,.*-:.     .        .        .        .       f^     .  13,31250 

Cost  of  operating,  at  $415  50  per  day,  ,  .  151,657  50 
Renewals  of  lamps,  .  .  .  .  .10,300  00 


Total  per  station,     .        .        .  .$253,29500 

For  the  four  stations,       .        .        .          1,013,180  00 

as  against  a  total  cost  per  annum  by  the  gas  system  of 
$1,973,760. 

At  a  rate  of  $1  12J  per  thousand  for  gas  the  gross  re- 
ceipts would  be  $1,511,100,   or  a  net  profit,   over  and 


COMMERCIAL  ASPECTS.  185 

above  7  per  cent,  upon  the  capital  invested,  of  $497,920, 
or  a  total  net  profit  of  30  per  cent. 

There  can  be  no  reasonable  doubt  that  the  electric 
light,  which  is  better  than  gas  light,  is  cheaper  than  gas 
light. 

In  turning  from  the  contemplation  of  this  subject,  it  is 
useful  to  consider  that  the  advances  made  in  electric 
lighting  within  a  very  few  months  are  of  a  nature  calcu- 
lated to  raise  our  anticipations  to  a  point  beyond  the 
warrant  of  actual  facts.  When  we  recall  to  mind  that 
from  the  discovery  by  Oersted,  in  1820,  that  an  electric 
current  would  deflect  a  magnetic  needle,  and  from  the 
later  discovery  by  Faraday  of  the  phenomena  of  mag- 
netic induction,  we  have  realized  the  electric  telegraph 
and  the  electric  light  of  to-day,  we  may  consistently  con- 
gratulate the  age  in  which  we  live ;  but  we  should  not 
be  sanguine  that  because  of  all  this  the  millennium  is 
close  at  hand.  The  application  of  electricity  to  public 
and  private  illumination  is  a  realization  of  the  near 
future  no  longer  to  be  questioned.  It  is  not  probable, 
however,  that  electricity  will  ever  entirely  supersede 
gas ;  indeed,  it  does  not  appear  that  illuminating  gas 
has  materially  affected  the  consumption  of  illuminating 
oils.  There  is  room,  and  will  doubtless  continue  to  be 
room,  for  all  methods  of  artificial  lighting,  and  it  is  not 
likely  that  for  many  years  to  come  we  shall  witness  any- 
thing more  than  the  extensive  use  of  electricity — public 
buildings  and  private  residences,  streets  and  squares 
better  illuminated  than  at  present,  and  the  new  form  of 
light  keeping  pace  with  the  progress  of  older  and  well- 
tried  institutions. 


INDEX. 


Armatures,  different  forms  of — 

Breguet,  53. 

Brash,  32. 

De  Meritens,  20. 

Edison,  41,  43. 

Frolich,  52. 

Gramme,  28,  29. 

Haf  ner-Alteneck,  37,  39,  48. 

Hochhausen,  41. 

Lontin,  20. 

Maxim,  31. 

Pacinotti,  35. 

Sawyer,  22,  41,  45,  46,  48. 

Seeley,  24. 

Siemens,  14,  15,  26,  37,  39,  48. 

Thomson  and  Houston,  41. 

Weston,  41. 
Artificial  resistances,  138. 

Bouliguine  lamp,  60. 
Brush  machine,  18,  33. 

Carbons — 

Behavior  of,  under  incandes- 
cence, 112. 

Carbide  forming  with  metallic 
connections,  75. 

Carbon  disintegrating,  75. 

Carbon  decomposing  in  a  trace 
of  combining  matter,  75. 

Connections  in  lamps,  96. 

Carre,  65. 


Carbons — 

Edison,  72. 

Jacquelin,  65. 

Mechanical  division  of,  65. 

Sawyer-Man,  68. 

Sawyer  Treating  Apparatus,  71. 

Swan,  72. 

Division  of  current  and  light,  115. 
Dynamo-electric  machines — 

Brush,  18,  33. 

Edison,  41. 

Gramme,  18,  27. 

Hafner-Alteneck,  18,  37. 

Hochhausen,  18,  41. 

Ladd,  11. 

Lontin,  20. 

Maxim,  31. 

Sawyer  distributor,  22. 

Sawyer,  41,  43. 

Seeley,  24. 

Siemens  alternating-current,  26. 

Siemens  (New),  37. 

Thomson  and  Houston,  41. 

Weston,  41. 

Electro-magnets,      different     forms 

of— 

Brush  t  33. 
De  Meritens,  19. 
Edison,  41. 
Gramme,  27. 


187 


188 


INDEX. 


Electro-magnets — 

Hafner-Alteneck,  37,  39. 
Lontin,  20. 
Maxim,  31. 
Pacinotti,  35. 
Sawyer,  22,  43. 
Seeley,  24. 
Siemens,  26,  37,  39. 
Wilde,  14,  15. 
Economy  of  the  electric  light.  10, 

21,  35,  38,  46,  Chap.  XII. 
Edison  switch,  139. 
"      machine,  41. 
"      lamp,  78. 

Faraday    (magneto-electric     induc- 
tion), 13,  185. 
Failures  of  old  lamps,  74. 

due  to  combustion  in  a  trace  of 

combining  matter,  75. 
the  carbide  forming  with  me- 
tallic contacts,  and  disintegra- 
tion, 75. 
Farmer's  lamp,  62. 

Gas  and  electric    light    compared, 

Chap.  XII. 
Generators  of  electricity — 

Principles  oi'  same  in  general, 

10,  13,  17. 
Brush  machine,  82. 
Gramme  machine,  28. 
New  Siemens  machine,  37-53. 
Accumulation  by  mutual  ac- 
tion, 17. 
Machines  of  the  magneto-electric 

type- 
Clarke,  11,  13. 
De  Meritens,  19. 
Faraday  (magneto-induction), 

13. 

Holmes,  13. 
Lontin,  20. 

Nollet  and  Van  Malderen,  1J, 
13. 


Generators  of  electricity — 
Pacinotti,  35. 
Pixii,  11,  13. 
Sawyer,  22. 
Saxton,  13. 
Siemens,  old,  14. 
Siemens    alternating-current, 

26. 

Wilde,  11,  14. 
Machines  of  the  dynamo-electric 

type- 
Brush,  18,  33. 
Edison,  41. 
Gramme,  18,  27. 
Hafner-Alteneck,  18,  37. 
Hochhausen,  18,  41. 
Ladd,  11. 
Lontin,  20. 
Maxim,  31. 

Sawyer  distributor,  23. 
Sawyer,  41,  43. 
Seeley,  24. 
Siemens    alternating-current, 

26. 

Siemens  (new),  37. 
Thomson  and  Houston,  41. 
Weston,  41. 

Heating  of  generators,   30,   32,  35, 

41,  43,  45,  47,  48. 
Heating  of  conductors,  173,  174. 

Incandescent  lamps — 
Bouliguine,  60. 
De  Moleyns,  77. 
Edison,  78. 
Farmer,  63. 
Fontaine,  60. 
Konn,  59. 
Kosloff,  60. 
Lodyguine,  58. 
Maxim,  82. 
Reynier,  56. 
Roberts,  78. 


INDEX. 


189 


Incandescent  lamps — 

Sawyer-Man,  83,  85,  86. 
Sawyer,  87,  89,  92,  100,  102. 
Shepard,  78. 
Starr-King,  57. 
•   Werdermann,  56. 
Connections  of,  96. 
Intensity   of  power  of,   46,  99, 

103, 179. 
Intensity    of     temperatures  of 

carbon  in,  55,  114. 

Jacquelin  carbons,  65. 
Konn  lamp,  59. 

Lontin's  machine,  20. 
Luminous  intensity  of  incandescent 
lamps  and  gas-burners,  99. 

Magneto-electric  machines — 

Clarke,  11,  13. 

De  Meriteris,  19. 

Faraday      (magneto-induction), 
13. 

Holmes,  13. 

Lontin ,  20. 

Nollet  and  Van  Malderen,  11, 13. 

Pacinotti,  35. 

Pixii.  11,  13. 

Sawyer,  22. 

Saxton,  13. 

Siemens,  old,  14. 

Siemens  alternating-current,  26. 

Wilde,  11,  14. 
Maxim's  lamp,  82. 

Nitrogen — 

Difficulty  of  obtaining  pure,  111. 
Drying  agents,  105. 
Preparation  of,  107,  108. 
Method  of  charging  lamps  with, 
110. 


Open-air  lamps,  56,  101. 
Operation  of  a  general  lighting  sys- 
tem, 150. 

Principles  of  electric  lighting — 
By  incandescence,  54. 
By  the  voltaic  arc,  9. 

Questions  of  economy  in  lighting, 
Chap.  XII. 

Regulators  and  switches,  129. 

Regulator  of  Maxim,  141. 

Regulator  of  Sawyer,  electro-magne- 
tic, 144. 

Regulator  of  Sawyer,  water,  146. 

Regulator  of  Thomson  and  Houston, 
14  >. 

/ 

Systems  of  subdivision,  118. 
Safety  devices,  Chap.  XI. 
Switches  of — 

Edison,  139. 

Maxim,  139. 

Sawyer-Man,  130. 

Sawyer,  133. 

Temperatures  of  incandescent  car- 
bons, 55,  114. 

Temperatures  of  Sawyer  machines, 
47,  48. 

Theory  of  the  arc,  9. 

Types  of  lamps,  55. 

Underground  conductors,  Chap.  XL 

Variations  in  intensity  of  light  by 
subdivision  of  current,  130. 

Wasting  of  the  incandescent  carbon, 
106. 


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HOTCHKISS,  JED.,  and  ALLAN,  WILLIAM.— The  Battle-Fields 
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Chancellorsville,  embracing  the  Operations  of  the  Army  of  Northern 
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HOWARD,  0.  R.— Earthwork  Mensuration  on  the  Basis  of  the 
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HUNTER,  Capt.  R.  P.— Manual  for  Quartermasters  and  Commis- 
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INDTJCTION-COILS.-How  Made  and  How  Used. 

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D.  VAN  NOSTRAND'S  CATALOGUE.  11 

INSTRUCTIONS  FOR  FIELD  ARTILLERY. 

Prepared  by  a  Board  of  Artillery  Officers.  To  which  is  added  the 
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ISHERWOOD,  B.  F.— Engineering    Precedents  for    Steam    Ma- 
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IVES,  Lieut.  R.  A.— Military  Law. 

A  Treatise  on  Military  Law,  and  the  Jurisdiction,  Constitution,  and 
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JANNETTAZ,  EDWARD.— A  Guide  to  the    Determination    of 
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Being  an  Introduction  to  Lithology.  '  Translated  from  the  French  by 
G.  W.  Plympton,  Professor  of  Physical  Science  at  Brooklyn  Polytechnic 
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JEFFERS,  Capt.  W.  N.,  U.  S.  N.— Nautical  Surveying. 

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JOMINI,  Gen.  BARON  DE.— Campaign  of  Waterloo. 

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JONES,  H.   CHAPMAN.-Text-Book    of   Experimental    Organic 

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JOYNSON,  F.  H.— The  Metals  used  in  Construction :  Iron,  Steel, 

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Designing  and  Construction  of  Machine  Gearing. 

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KANSAS  CITY  BRIDGE,  THE. 

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KELTON,  Gen.  J.  C.— New  Bayonet  Exercise. 

A  New  Manual  of  the  Bayonet,  for  the  Army  an<1  Militia  of  the  United 
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12  D.  VAN  NO  STRAND'S  CATALOGUE. 

KING,  W.  H.— Lessons  and  Practical  Notes  on  Steam, 

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KIRKWOOD,  JAS.  P.— Report  on  the  Filtration  of  River  Waters 
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LARRABEE,  0.  S.— Cipher  and  Secret  Letter  and  Telegraphic 
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LAZELLE,  Capt.  H.  M.,  U.  S.  A.-One  Law  in  Nature. 

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LECOMTE,  FERDINAND.— The  War  in  the  United  States. 

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LE  GAL,  Col.  EUGENE.— School  of  the  Guides. 

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LEND Y,  Capt.— Maxims  and  Instructions  on  the  Art  of  War. 

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LEVY,  Com.  U.  P.— Manual  of  Internal  Rules  and  Regulations 
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LIEBER,  FRANCIS,  LL.D.— Instructions  for  Armies. 

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LOCK,  C.  G.,  WIGNER,  G.  W.,  and  HARLAND,  R.  H.-Sugar 
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D.    VAN  NOSTRAND'S  CATALOGUE.  13 

LORING,  A.  E.— A  Hand-Book   on  the   Electro-Magnetic   Tele- 
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LUCE,  Com.  S.  P.— Text-Book  of  Seamanship. 

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Naval  Light  Artillery. 

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MacCORD,  Prof.  C.  W.— A  Practical  Treatise  on  the  Slide-Valve 
by  Eccentrics, 

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and  explaining  the  practical  processes  'of  laying  out  the  movements, 
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McCLELLAN,  Gen.  GEO.  B.— Report  of  the  Army  of  the  Potomac, 
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8vo,  cloth., .... 1  00 

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McCULLOCH,  Prof.  R.  S.— Elementary  Treatise  on  the  Mechani- 
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MANUAL  OF  BOAT  EXERCISE 

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MENDELL,  G.  H.— Military  Surveying. 

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MERRILL,  Col.  WM.  E.,U.  S.  A.— Iron  Truss  Bridges  for  Railroads. 

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MICHIE,  Prof.  P.  S.— Elements  of  Wave  Motion  relating  to  Sound 

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MINIFIE,  WM.— Mechanical  Drawing. 

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No  ydung  Mechanic,  such  as  a  Machinist,  Engineer,  Cabinet-maker,  Mill- 
wright, or  Carpenter,  should  be  without  it." — Scientific  American. 

Geometrical  Drawing. 

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MODERN  METEOROLOGY. 

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MONROE,  Col.  J.— Light  Infantry  Company  and  Skirmish  Drill 
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MOORE,  FRANK.— The  Rebellion  Record. 

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MORRIS,  E.— Easy  Rules  for  the  Measurement  of  Earthworks, 

by  M:eans  of  the  Prismoidal  Formula. 
78  illustrations.    8vo,  cloth 1  50 

MORRIS,  Gen.  WM.  H.— Field  Tactics  for  Infantry. 

Illustrated.     18mo,  cloth 75 

Infantry  Tactics. 

2  vols.  24mo 2  00 

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